The National Academies Press

<!doctype html> <html lang="en"> <head> <meta charset="UTF-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="cache-control" content="no-cache"/> <title>The National Academies Press</title> <meta name="description" content="The National Academies Press (NAP) publishes authoritative reports issued by The National Academies of Science, Engineering, and Medicine (NASEM)."> <meta name="keywords" content="science policy research, health, medicine, bookstore, agriculture, medical ethics, behavioral social sciences, biology, economics, chemistry, earth, education, engineering, environment, information technology, math, physics, national security, space, textbooks, public policy"> <link rel="canonical" href="https://nap.nationalacademies.org"> <meta property="fb:page_id" content="37495980935" /> <link rel="alternate" type="application/rss+xml" title="New from the National Academies Press" href="https://nap.nationalacademies.org/rss/new.xml"> <link href="https://plus.google.com/111471144526792699277" rel="publisher" /> <link rel="stylesheet" href="https://maxst.icons8.com/vue-static/landings/line-awesome/line-awesome/1.3.0/css/line-awesome.min.css"> <script> // if (document.location.hostname.search(/nap\.edu$/) < 0) { // url = "http://www.na" + "p.edu" + document.location.pathname + document.location.search // document.location.replace(url); // } </script>  <meta name="alexaVerifyID" content="02J2SepmgvpkhVXcfeE98cX3HKs" /> <link href="//nap.nationalacademies.org/stylesheets/nasem-nap.css" rel="stylesheet" type="text/css"> <link href="//nap.nationalacademies.org/stylesheets/topnav-lite-min.css" rel="stylesheet" type="text/css" /> <link href="//nap.nationalacademies.org/stylesheets/component.css" rel="stylesheet" type="text/css" />  <script src="/includes/js/jquery-3.5.1.min.js"></script> <script src="/includes/js/jquery.dotdotdot.min.js" type="text/javascript"></script>    <script type="text/javascript"> var $mcGoal = {'settings':{'uuid':'eaea39b6442dc4e0d08e6aa4a','dc':'us4'}}; (function() { var sp = document.createElement('script'); sp.type = 'text/javascript'; sp.async = true; sp.defer = true; sp.src = ('https:' == document.location.protocol ? 'https://s3.amazonaws.com/downloads.mailchimp.com' : 'http://downloads.mailchimp.com') + '/js/goal.min.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(sp, s); })(); </script>  <script> window.dataLayer = window.dataLayer || [];dataLayer.push({ 'pageTitle' : "Home", 'loginStatus' : "guest", 'form' : "subscribe" }); </script> <script>(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start': new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0], j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src= 'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f); })(window,document,'script','dataLayer','GTM-N9MJ23');</script>  <script async src="https://www.googletagmanager.com/gtag/js?id=AW-1071160892"></script> <script> window.dataLayer = window.dataLayer || []; function gtag(){dataLayer.push(arguments);} gtag('js', new Date()); gtag('config', 'AW-1071160892'); gtag('config', 'AW-1071160892'); </script> <script id="mcjs">!function(c,h,i,m,p){m=c.createElement(h),p=c.getElementsByTagName(h)[0],m.async=1,m.src=i,p.parentNode.insertBefore(m,p)}(document,"script","https://chimpstatic.com/mcjs-connected/js/users/eaea39b6442dc4e0d08e6aa4a/208cb1a4b431cae38b54bdb6f.js");</script>  <style>.async-hide { opacity: 0 !important} </style> <script> (function(a,s,y,n,c,h,i,d,e){s.className+=' '+y;h.start=1*new Date; h.end=i=function(){s.className=s.className.replace(RegExp(' ?'+y),'')}; (a[n]=a[n]||[]).hide=h;setTimeout(function(){i();h.end=null},c);h.timeout=c; })(window,document.documentElement,'async-hide','dataLayer',4000, {'GTM-PXVRTFR':true}); </script> <script> (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){ (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o), m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m) })(window,document,'script','https://www.google-analytics.com/analytics.js','ga'); ga('create', 'UA-2382644-4', 'auto'); // Update tracker settings ga('require', 'GTM-PXVRTFR'); // Add this line </script> <link rel="preload" href="/stylesheets/vendor/bootstrap-3.0.3/fonts/glyphicons-halflings-regular.woff" as="font" crossorigin="anonymous"/> <link rel="preload" href="/stylesheets/fonts/icomoon.woff" as="font" crossorigin="anonymous"/> <link rel="stylesheet" href="/stylesheets/vendor/bootstrap-3.0.3/bootstrap.min.css">  <link rel="stylesheet" href="/stylesheets/naphome.css" /> <link rel="stylesheet" href="/stylesheets/fonts/icomoon.woff" /> <style> .book-row.row { background: #fff; } .top-rows { padding:20px 10px } .well.rfy-titles { height:100%!important } .well.rfy-titles > .book-tile { padding:15px } .well.rfy-titles > .book-tile { padding:15px } .whitewrapper { -webkit-box-shadow:none*/ -moz-box-shadow: none; box-shadow:none; padding:10px; font-family:'archivo_narrowregular',helvetica,sans-serif; margin-bottom:10px } .whitewrapper.bbt-btn { background:none; color:#336699; border:none; min-height:52px; margin-top:10px } .whitewrapper.bbt-btn:hover { background:none; color:#336699; border:none; } .ww-innerbbt { font-size:16px; top:24px } .ww-innerbbt:hover { border-bottom: 4px solid #1d1646; } .mynap-btn-off { top:11px } .btn-searchhome { float:right; display:inline; width:26%; font-size: 14px; border:none; border-radius:5px; height:52px; text-wrap:suppress; word-break:keep-all; overflow:hidden } .icon-search { font-size:18px; } .col-xs-1, .col-sm-1, .col-md-1, .col-lg-1, .col-xs-2, .col-sm-2, .col-md-2, .col-lg-2, .col-xs-3, .col-sm-3, .col-md-3, .col-lg-3, .col-xs-4, .col-sm-4, .col-md-4, .col-lg-4, .col-xs-5, .col-sm-5, .col-md-5, .col-lg-5, .col-xs-6, .col-sm-6, .col-md-6, .col-lg-6, .col-xs-7, .col-sm-7, .col-md-7, .col-lg-7, .col-xs-8, .col-sm-8, .col-md-8, .col-lg-8, .col-xs-9, .col-sm-9, .col-md-9, .col-lg-9, .col-xs-10, .col-sm-10, .col-md-10, .col-lg-10 { position: relative; min-height: 1px; padding-left: 10px; padding-right: 10px; } /*Carousel Styles*/ .img-responsive,.thumbnail>img,.thumbnail a>img,.carousel-inner>.item>img,.carousel-inner>.item>a>img { display:block; width: auto !important; height:auto } .ft h4 { font-family: 'lato', helvetica, sans-serif; font-size: 15px; color: #666; height: 70px; padding-top: 20px; } @media screen and (max-width:556px) { .btn-searchhome { border-radius:4px; height:43px } .hidden-xxs { display:none } } @media screen and (min-width:768px) { .carousel-control .glyphicon-chevron-left,.carousel-control .glyphicon-chevron-right,.carousel-control .icon-prev,.carousel-control .icon-next { width:30px; height:30px; margin-top:-15px; margin-left:-0px; font-size:30px } .carousel-indicators { bottom:0 } } @media screen and (max-width: 768px) { .ww-innerbbt { font-size:18px; top:18px } .mynap-btn-off { top:2px } .well.rfy-titles > .book-tile { padding:20px } h4.rfymore { height:40px; margin-bottom:0 } .icon-search { font-size:23px!important } .btn-searchhome { border-radius:4px; height:48px } .carousel-caption h1 { color: #fff; margin-bottom: 20px; font-size: 2.2rem; } } .page-header .page-header__title { color:#222; color:var(--color-neutral--charcoal); font-size:1.78rem; font-weight:900; font-weight:var(--lato--black); margin-bottom:1.5rem; max-width:100% } .page-header__description { font-size: 1.3em; line-height: 1.75; } .sub-footer { background: #fff; background-image: linear-gradient(180deg, #f3f1eb 0, rgba(243,241,235,0) 250px); padding: 30px 0px 30px 0px; } #email { width: 98%; } .nav-wrap { margin: 50px auto; background-color: transparent; border-top: 1px solid rgb(204,204,204); border-bottom: none; } #local-nav-nap { margin: 0 auto; list-style: none; position: relative; width: 100%; } #local-nav-nap li { display: inline; } #local-nav-nap li a { color: rgb(51,51,51); color: var(--color-neutral--jet); display: block; font-size: 12px; font-weight: 700; min-width: 3em; max-width: 200px; padding: 1.5em 2.2em; position: relative; text-align: center; text-decoration: none; text-transform: uppercase; transition: color .15s; white-space: nowrap; float: left; } #local-nav-nap li a:hover { color: #1d1646; } #magic-line { position: absolute; bottom: -2px; left: 0; width: 100px; height: 7px; background: #1d1646; } .local-nav { border-color: rgb(204,204,204); border-color: var(--color-neutral--pastel); border-width: 1px 0 0; display: -webkit-flex; display: flex;local-nav-nap -webkit-justify-content: flex-start; justify-content: flex-start; max-width: 100%; padding-top: .4rem; } .local-nav__link { color: rgb(51,51,51); color: var(--color-neutral--jet); display: block; font-size: 12px; font-weight: 400; min-width: 4rem; max-width: 200px; padding: .75rem 1.75rem; position: relative; text-align: center; text-decoration: none; text-transform: uppercase; transition: color .15s; white-space: nowrap; } .local-nav__link.is-active::after, .local-nav__link.is-hovered::after { background-color: #1d1646; } .local-nav__link::after { content: ""; background-color: transparent; display: block; height: 7px; left: -2px; position: absolute; top: -1em; transition: background-color .15s; width: 101%; } .prepubbanner { bottom: 23px; } </style> <style>pre { background-color: transparent !important; }</style> </head> <body>  <noscript><iframe src="https://www.googletagmanager.com/ns.html?id=GTM-N9MJ23" height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript>  <a name="top" id="top"></a> <a href="#content" class="sr-only sr-only-focusable">Skip to main content</a> <style> body { overflow-x: hidden; } #lowerMenu { background: #fff } .global-nav--local .mega-menu { display: block; -webkit-transform: translateY(0em); transform: translateY(0em); } .global-nav--local.search-is-hidden .mega-menu { display: none; -webkit-transform: translateY(0em); transform: translateY(0em); } .global-nav .container:not(.mega-menu__header) { padding: 0rem; padding-top: 0rem; padding-right: 0rem; padding-top: 0.5rem; padding-right: 1rem; } .global-nav__controls { top: .3rem; padding-right: 20px; } .global-nav--local .global-nav__links { -webkit-transform: translateY(0); transform: translateY(0); max-width: 75%; float: right; background: #fff; } .global-nav__links ul { display: -webkit-flex; display: flex; -webkit-justify-content: flex-end; justify-content: flex-end; margin-top: .5rem; } .global-nav--local.menu-is-hidden .global-nav__links { opacity: 0; -webkit-transform: translateY(0.5em); transform: translateY(0.5em); visibility: hidden; } #header-large { max-width: 1180px; margin: 0; padding: 0 0; -webkit-box-shadow: none; -moz-box-shadow: none; box-shadow: none; flex-wrap: nowrap; position: absolute; top: 113px; text-align: right; width: 100%; right: 0; } #header-large .user-links { white-space: nowrap; display: inline-flex; margin: 0; padding: 0; background: #fff; z-index: 0; list-style: none; min-width:500px; } .user-links li { margin-right: 7%; } .user-links li a { font-size: 10px; text-align: left; text-transform: uppercase; color: #000; } #header-large a.site-links { margin-right: 15px; color: #000; padding-left: 0px; padding-right: 5px; font-size: 12px; text-transform: uppercase; } .site-links:hover { text-decoration: underline; } nav#sitelinks-wide { position: absolute; top: 16px; } #sitelinks-wide ul { display: flex; justify-content: space-between; margin: 0; padding: 0; } #sitelinks-wide ul li { #sitelinks-mobile { display: none; } white-space: nowrap; } #sitelinks-mobile { display: none; } .user-links li a:hover { text-decoration: underline; } .dropdown-menu { position: absolute; top: 100%; left: 10px; z-index: 9999999; display: none; float: left; min-width: 160px; padding: 5px 0; margin: 2px 0 0; list-style: none; font-size: 14px; background-color: #ffffff; border: 1px solid #cccccc; border: 1px solid rgba(0, 0, 0, 0.15); border-radius: 4px; -webkit-box-shadow: 0 6px 12px rgba(0, 0, 0, 0.175); box-shadow: 0 6px 12px rgba(0, 0, 0, 0.175); background-clip: padding-box; } #dropdownMenuButton { border: 1px solid #ccc; font-size: 14px; font-weight: 700; } .dropdown #dropdownMenuButton:after { content: '\02795'; /* Unicode character for "plus" sign (+) */ font-size: 13px; color: #777; float: right; margin-left: 5px; } .dropdown.open #dropdownMenuButton:after { content: "\2796"; /* Unicode character for "minus" sign (-) */ } li.naphelp { display: block;} @media (max-width: 930px) { #header-large { right: 80px; } #header-large .user-links { min-width:100px; } nav#sitelinks-wide { display: none; } #sitelinks-mobile { display: block; position: absolute; top: -10px; left: 107px; } #sitelinks-wide ul { display: block; } #sitelinks-wide ul li { margin-right: 0%; white-space: nowrap; } .dropdown-item { display: block; width: 100%; padding: .25rem 1.5rem; clear: both; font-weight: 400; color: #212529; text-align: inherit; white-space: nowrap; background-color: transparent; border: 0; text-align: left; } .dropdown.nap-mega-menu.mega-dropdown { display: none;} li.naphelp { display: none;} } .global-nav__links { display: none; opacity: 1; transition: opacity .15s, -webkit-transform .15s; transition: opacity .15s, transform .15s; transition: opacity .15s, transform .15s, -webkit-transform .15s; } .global-nav--local .global-nav__links { -webkit-transform: translateY(0); transform: translateY(0); } .global-nav--local.menu-is-hidden .global-nav__links { opacity: 0; -webkit-transform: translateY(0.5em); transform: translateY(0.5em); } .global-nav__links ul { display: -webkit-flex; display: flex; -webkit-justify-content: flex-end; justify-content: flex-end; margin-top: 1rem; } .global-nav__links li:hover .global-nav__link>span::before, .global-nav__links li:focus-within .global-nav__link>span::before, .global-nav__links .global-nav__link.is-active>span::before, .global-nav__links .global-nav__link:hover>span::before, .global-nav__links .global-nav__link:focus>span::before { background-color: #1C143D; ; } .global-nav__links li:hover .global-nav__link>span::before::after, .global-nav__links li:focus-within .global-nav__link>span::before::after, .global-nav__links .global-nav__link.is-active>span::before::after, .global-nav__links .global-nav__link:hover>span::before::after, .global-nav__links .global-nav__link:focus>span::before::after { opacity: 1; } @media screen and (min-width: 65em) { .global-nav__links { display: block; } .global-nav__links>ul>li:last-of-type .global-nav__link { margin-right: -1.25em; } } .global-nav__link { position: relative; display: block; padding: .75em 1.5em .5em; color: rgb(34, 34, 34); color: var(--color-neutral--charcoal); border-bottom: 5px solid transparent; /*font-size: .885rem;*/ font-weight: 700; font-weight: var(--lato--bold); text-decoration: none; transition: color .15s; } .global-nav__link>span { position: relative; } .global-nav__link>span::before { content: ""; position: absolute; bottom: -.5em; left: 0; width: 100%; height: 5px; background-color: transparent; transition: background-color .15s; } .global-nav__dropdown { position: absolute; top: calc(100% + 1em); left: 50%; display: none; width: 600px; background-color: rgb(255, 255, 255); background-color: var(--color-neutral--white); box-shadow: 0 5px 15px rgba(34, 34, 34, .25); box-shadow: 0 5px 15px var(--box-shadow--charcoal); -webkit-transform: translateX(-50%); transform: translateX(-50%); z-index: 20; } .global-nav__dropdown::before { content: ""; position: absolute; top: -1em; left: 0; display: block; width: 100%; height: 1em; } .global-nav__dropdown .dropdown__left { position: relative; min-height: 260px; width: 40%; padding: 1.5rem; background: rgb(255,255,255); background: -moz-linear-gradient(180deg, rgba(255,255,255,1) 0%, rgba(73,69,104,1) 0%, rgba(0,0,0,1) 100%, rgba(195,228,228,1) 100%); background: -webkit-linear-gradient(180deg, rgba(255,255,255,1) 0%, rgba(73,69,104,1) 0%, rgba(0,0,0,1) 100%, rgba(195,228,228,1) 100%); background: linear-gradient(180deg, rgba(255,255,255,1) 0%, rgba(73,69,104,1) 0%, rgba(0,0,0,1) 100%, rgba(195,228,228,1) 100%); filter: progid:DXImageTransform.Microsoft.gradient(startColorstr="#ffffff",endColorstr="#c3e4e4",GradientType=1); } .global-nav__dropdown .dropdown__left a { display: block; color: rgb(255, 255, 255); color: var(--color-neutral--white); font-weight: 400; font-weight: var(--lato--regular); transition: color .15s; font-size: 16px; } .global-nav__dropdown .dropdown__left a:hover, .global-nav__dropdown .dropdown__left a:focus, .global-nav__dropdown .dropdown__left a:active { color: rgb(246,210,0); color: var(--color-yellow--pure); } .global-nav__dropdown .dropdown__left ul { -webkit-flex-direction: column; flex-direction: column; } .global-nav__dropdown .dropdown__left li a { padding: .5em 0; line-height: 1.4; } .global-nav__dropdown .dropdown__left--default { position: absolute; top: 0; right: 0; bottom: 0; left: 0; overflow: hidden; background-color: rgb(243, 241, 235); background-color: var(--color-brown--bone); } .global-nav__dropdown .dropdown__left--default img { width: 100%; height: auto; /* stylelint-disable max-nesting-depth */ /* stylelint-enable max-nesting-depth */ } @supports (object-fit: cover) { .global-nav__dropdown .dropdown__left--default img { height: 100%; object-fit: cover; } } .global-nav__dropdown .dropdown__right { width: 60%; padding: 1.5rem; } .global-nav__dropdown .dropdown__right .button { margin-top: 2em; text-shadow: none; } .global-nav__dropdown .dropdown__right a { color: rgb(0, 89, 145); color: var(--color-blue--bahama); text-decoration: none; transition: color .15s; } .global-nav__dropdown .dropdown__right a:hover, .global-nav__dropdown .dropdown__right a:focus { color: rgb(33,23,71); color: var(--color-blue--imperial); text-decoration: underline; } .rm-dropdown:hover::after, .rm-dropdown:focus::after { visibility: hidden; } .has-dropdown { position: relative; } .has-dropdown::after { content: ""; position: absolute; top: calc(100% + 3px); left: 50%; width: 26px; height: 15px; background-image: url(data:image/png;base64,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); background-repeat: no-repeat; -webkit-transform: translateX(-50%); transform: translateX(-50%); visibility: hidden; } .has-dropdown:hover::after, .has-dropdown:focus::after { visibility: visible; } .has-dropdown:hover .global-nav__dropdown { display: -webkit-flex; display: flex; } .has-dropdown:focus-within .global-nav__dropdown { display: -webkit-flex; display: flex; } .has-dropdown:nth-last-of-type(-n+3) .global-nav__dropdown { left: auto; -webkit-transform: none; transform: none; } .has-dropdown:nth-last-of-type(3) .global-nav__dropdown { right: -200%; } .has-dropdown:nth-last-of-type(2) .global-nav__dropdown { right: -90%; } .has-dropdown:last-of-type .global-nav__dropdown { right: 5%; } .global-nav__links { z-index: 5; } header.global-nav { height: 150px; } .button.button--secondary.button--outline.button--icon { font-size: 12px; padding-right: 40px; } .button.button--icon svg { height: 2.5em; position: absolute; top: 50%; left: 60%; -webkit-transform: translate(-50%, -50%); transform: translate(-50%, -50%); width: 24px; } .controls__search, .controls__menu, .controls__nav { font-size: 12px; } .global-nav__menus--upper { display: -webkit-flex; display: flex; -webkit-justify-content: space-between; justify-content: space-between; margin-bottom: 2rem; } .global-nav__link { font-size: 16px; } .global-nav__links ul { display: -webkit-flex; display: flex; -webkit-justify-content: flex-end; justify-content: flex-end; margin-top: 5px; list-style: none; } .invert { background: #000; color: #fff; } .controls__nav .menu-off { display: inline; } .controls__nav .menu-on { display: none; } .controls__nav.invert .menu-off { display: none } .controls__nav.invert .menu-on { display: inline; } .mega-menu { background-color: rgb(243, 241, 235); background-color: var(--color-brown--bone); position: fixed; top: 0; right: 0; bottom: 0; left: 0; overflow: scroll; z-index: 9999999; } .mega-menu .mega-menu__header { display: -webkit-flex; display: flex; -webkit-justify-content: space-between; justify-content: space-between; -webkit-align-items: center; align-items: center; padding-top: 1rem; } .mega-menu__content .search-form__container { position: relative; max-width: 70em; margin: 0 auto; } #search .global-nav__logo { position: absolute; top: 1em; } .sf-top { margin-top: 50px; } #searchFormNAP { display: block; height: 100px; } a:hover, a:focus { color: #1C143D; text-decoration: underline; } #fixedfooter a:hover, #fixedfooter a:focus { color: #fff; text-decoration: underline; } .btn-blueflat.btn-searchhome.hide-xs { display: none; } .mega-menu__content { margin-top: 50px; margin-left: 7px; } .accordion__title.faq__accordion__title .flex.justify-between { display: inherit; } .global-nav__logo { margin: 0px !important; position: absolute; left: 15px; top: 25px; height: 55px; } .global-nav__link:hover { text-decoration: none; } @media screen and (min-width: 65em) { .mega-menu__content .search-form { padding: 1em 0px 3em 0em; } } @media (min-width: 45rem) { .global-nav__logo {} } @media (max-width: 480px) { .global-nav__logo { margin: 0px !important; position: absolute; left: 15px; top: 12px; } } /* Style the buttons that are used to open and close the accordion panel */ #mobile-menu button.accordion, #mobile-menu button.no-accordion { letter-spacing: 1px; text-align: left; color: #4148C2; font-size: 1.1em; font-weight: 700 !important; font-family: 'lato', helvetica, sans-serif; padding: 15px 0px 15px 0px; border-top: none !important; border-bottom: .5px solid rgb(221, 213, 199) !important; cursor: pointer; width: 100%; } .mega-menu__content .accordion { border: 0; font-weight: 700; } #mobile-menu .accordion:after { content: '\02795'; /* Unicode character for "plus" sign (+) */ font-size: 13px; color: #777; float: right; margin-left: 5px; } #mobile-menu button.active:after { content: "\2796"; /* Unicode character for "minus" sign (-) */ } /* Add a background color to the button if it is clicked on (add the .active class with JS), and when you move the mouse over it (hover) */ #mobile-menu button.active, #mobile-menu button.accordion:hover { background-color: transparent; } /* Style the accordion panel. Note: hidden by default */ #mobile-menu .panel { padding: 0 0; background-color: transparent; max-height: 0; box-shadow: 0 !important; overflow: hidden; transition: max-height 0.2s ease-out; margin: 0px !important; border: 0 !important; } #mobile-menu .panel ul li { margin: 0px 0px; padding-left: 0px; } #mobile-menu .panel ul { margin-top: 10px; margin-bottom: 10px; padding-left: 0px; } #mobile-menu .panel ul li { line-height: 2; } #mobile-menu .panel ul li a { color: #000; text-decoration: underline; cursor: pointer; } .controls__menu-mobile { text-transform: uppercase; } .controls__menu-mobile svg { fill: #222; fill: var(--color-neutral--charcoal); width: 1.75rem; height: 1.75rem; } .cart-badge { display: inline-block; text-align: center; line-height: 1; background: #7899F2; color: white; font-weight: bold; border-radius: 20px; padding: 3px 6px; margin-left: 3px; } @media screen and (min-width: 65em) { #mobile-menu .controls__menu { display: inline; } } @media screen and (max-width: 65em) { #mobile-menu .controls__menu svg { display: inline; } } /*NAP mega menu dropdown*/ li.nap-mega-menu.mega-dropdown { position: static !important; width:100% !important; } .nap-mega-menu .mega-dropdown-menu { padding: 20px 0px; box-shadow: none; -webkit-box-shadow: none; margin-top: 10px !important; box-shadow: 0 5px 15px var(--box-shadow--charcoal); transform: none !important; top: 100% !important; } .nap-mega-menu .mega-dropdown-menu > li > ul.browse-col { padding: 0; margin: 0; width: 100%; } .nap-mega-menu .mega-dropdown-menu > li > ul > li { list-style: none; } .nap-mega-menu .mega-dropdown-menu > li > ul > li > a { display: block; padding: 3px 20px; clear: both; font-weight: normal; line-height: 1.428571429; color: #4148C2; white-space: normal; font-size: 14px; text-transform: none; } .nap-mega-menu .mega-dropdown-menu > li ul > li > a:hover, .nap-mega-menu .mega-dropdown-menu > li ul > li > a:focus { text-decoration: none; color: #444; background-color: #f5f5f5; } .nap-mega-menu .mega-dropdown-menu .dropdown-header a { color: #4148C2; font-size: 14px; font-weight: 900 !important; text-align: left; text-transform: uppercase !important; padding: 0px; margin-bottom: 7px; } .nap-mega-menu .mega-dropdown-menu form { margin:3px 20px; } .nap-mega-menu .mega-dropdown-menu .form-group { margin-bottom: 3px; } .nap-mega-menu .vertical-divider { border-left: 1px solid #ccc; } .nap-mega-menu .mega-dropdown-menu > li.d-flex { display: inline-flex !important; margin-right: 0 !important; justify-content: space-between; flex-wrap: nowrap !important; flex-direction: row !important; } #nap-mega-menu-inner { justify-content: space-between; align-content:start; } #nap-mega-menu-inner li.browse-col { width: 22%; } </style> <header class="global-nav global-nav--local menu-is-hidden search-is-hidden" id="lowerMenu"> <div class="container flex justify-between">  <div aria-hidden="true" class="mega-menu" id="search"> <div data-lock=""> <div class="container mega-menu__header"> <div class="global-nav__logo"> <a class="navbar-brand js-scroll-trigger" href="https://www.nationalacademies.org/"> <svg xmlns="http://www.w3.org/2000/svg" id="nasemLogo" data-name="nasemLogo" viewBox="0 0 360 66.64"> <defs/> <path d="m4.26 8.63 19.56 20.49V1.72h-3.47v18.93L.8.16v27.32h3.46V8.63zM32.55 27.48h3.83l8.15-19.2 7.93 18.99.09.21h3.82L44.62 0 32.55 27.48zM175.05 27.48h3.83l8.16-19.2 7.93 18.99.08.21h3.83L187.12 0l-12.07 27.48zM68.23 27.48h3.47V5.03h7.72V1.72H60.51v3.31h7.72v22.45zM90.08 1.72h3.46v25.76h-3.46z" class="cls-2"/> <path d="M157.14 38.67A13.39 13.39 0 1 0 143.75 52a13.21 13.21 0 0 0 13.39-13.33Zm-3.54 0a9.85 9.85 0 1 1-9.85-10 9.93 9.93 0 0 1 9.85 10Z" class="cls-2" transform="translate(-24.97 -24.05)"/> <path d="m146.56 8.63 19.56 20.49V1.72h-3.47v18.93L143.1.16v27.32h3.46V8.63zM210.95 1.72h-3.46v25.76h13.8v-3.31h-10.34V1.72z" class="cls-2"/> <path d="M67.41 63A13.13 13.13 0 0 0 54 76.37a13 13 0 0 0 13.26 13.24A13.48 13.48 0 0 0 75 87.1l.14-.1v-4.46l-.58.58a10.91 10.91 0 0 1-2.81 2 10 10 0 0 1-4.51 1.13c-6.74 0-9.77-5.78-9.77-9.89a9.82 9.82 0 0 1 9.74-10.11 10.44 10.44 0 0 1 4.18.94 12 12 0 0 1 3.17 2.27l.58.58v-4.41l-.13-.1a12.1 12.1 0 0 0-7.6-2.53ZM130 66.4a14 14 0 0 0-9.47-3h-5.45v25.75h5.42c4.25 0 6.88-.83 9.39-3a12.32 12.32 0 0 0 4.52-9.89A12.54 12.54 0 0 0 130 66.4Zm-2.39 17.26a10.37 10.37 0 0 1-7 2.18h-2.11V66.7h2.11c6.21 0 10.22 3.77 10.22 9.59a9.23 9.23 0 0 1-3.25 7.37Z" class="cls-2" transform="translate(-24.97 -24.05)"/> <path d="M119.94 65.11h15.33V61.8h-11.86v-9.07h10.38v-3.31h-10.38v-6.76h11.86v-3.32h-15.33v25.77zM201.26 65.11h15.33V61.8h-11.86v-9.07h10.37v-3.31h-10.37v-6.76h11.86v-3.32h-15.33v25.77zM158.66 58.65l-9.79-21.53-4.42 27.99h3.56l2.36-16.59 8.25 18.12 8.35-18.12 2.25 16.59h3.56l-4.14-28.03-9.98 21.57zM184.29 39.34h3.46V65.1h-3.46z" class="cls-2"/> <path d="M263.7 76.76a12.7 12.7 0 0 0-4-2.44l-2.42-1a8 8 0 0 1-2.53-1.51 2.32 2.32 0 0 1-.83-1.94c0-2.11 1.56-3.53 3.87-3.53a4.18 4.18 0 0 1 2.61.79 5.51 5.51 0 0 1 1.37 1.77l.17.34 2.8-1.85-.14-.27a7.79 7.79 0 0 0-2.56-2.91 7.16 7.16 0 0 0-4.18-1.21c-4.34 0-7.37 2.8-7.37 6.8a5.53 5.53 0 0 0 1.83 4.35 10.74 10.74 0 0 0 3.24 2l2.44 1.17a10.81 10.81 0 0 1 2.94 1.68 3.39 3.39 0 0 1 1.13 2.68A4.8 4.8 0 0 1 254 85a5.6 5.6 0 0 1-1.42-3l-.05-.39-3.4.94.07.32a9.51 9.51 0 0 0 2.43 4.61 7.73 7.73 0 0 0 5.69 2.13 7.9 7.9 0 0 0 8.28-8 6.38 6.38 0 0 0-1.9-4.85Z" class="cls-2" transform="translate(-24.97 -24.05)"/> <path d="M0 65.11h3.83l8.16-19.21 7.92 19 .09.21h3.83L12.07 37.63 0 65.11zM57.37 65.11h3.83l8.15-19.21 7.93 19 .08.21h3.83L69.44 37.63 57.37 65.11z" class="cls-2"/> <path d="M292 26.45a3.91 3.91 0 0 0-1.07-.14 2.94 2.94 0 0 0-1.74.52 1.71 1.71 0 0 0-.72 1.47 2.36 2.36 0 0 0 .63 1.7 9.45 9.45 0 0 0 1.9 1.38 15.52 15.52 0 0 1 1.45 1 4.28 4.28 0 0 1 .94 1.12 2.87 2.87 0 0 1 .38 1.51 3.57 3.57 0 0 1-.57 2 3.79 3.79 0 0 1-1.6 1.34 5.79 5.79 0 0 1-2.39.47 9.63 9.63 0 0 1-2.22-.25 4.15 4.15 0 0 1-1.41-.52l.39-2.49H287l.11 1.84a2.93 2.93 0 0 0 .92.39 5 5 0 0 0 1.16.14 3.39 3.39 0 0 0 2-.6 1.94 1.94 0 0 0 .83-1.68 2.25 2.25 0 0 0-.56-1.54 7.66 7.66 0 0 0-1.7-1.32c-.6-.39-1.1-.75-1.51-1.07a4.43 4.43 0 0 1-1-1.2 2.94 2.94 0 0 1-.43-1.59 3.08 3.08 0 0 1 .57-1.85 3.58 3.58 0 0 1 1.55-1.23 5.17 5.17 0 0 1 2.13-.43 7.84 7.84 0 0 1 2 .21 4 4 0 0 1 1.25.51l-.4 2.31h-.95l-.14-1.68a2.39 2.39 0 0 0-.83-.32ZM300.27 29.79a2.2 2.2 0 0 0-1.53.62 4.15 4.15 0 0 0-1.06 1.74 8 8 0 0 0-.38 2.55 4.11 4.11 0 0 0 .5 2.24 1.6 1.6 0 0 0 1.42.74 2.71 2.71 0 0 0 1.25-.27 5.56 5.56 0 0 0 1.15-.81l.35.64a4.42 4.42 0 0 1-1.31 1.08 3.78 3.78 0 0 1-2 .5 2.76 2.76 0 0 1-2.31-1 4.51 4.51 0 0 1-.83-2.9 7.35 7.35 0 0 1 .6-2.87 6 6 0 0 1 1.77-2.38 4.27 4.27 0 0 1 2.77-.95 5.7 5.7 0 0 1 1.06.11 3.31 3.31 0 0 1 .92.3l-.48 1.7-.29-.11a2.91 2.91 0 0 0-1.6-.93ZM306.13 37.31a.54.54 0 0 0 .08.33.22.22 0 0 0 .2.11.74.74 0 0 0 .39-.12 2.88 2.88 0 0 0 .5-.4l.23.42a3.34 3.34 0 0 1-.78.77 2 2 0 0 1-1.23.4 1.3 1.3 0 0 1-.89-.27.9.9 0 0 1-.26-.81c0-.3.18-1.43.46-3.41q.24-1.59.6-4.23l-1.09-.4.11-.6 2.49-.4.38.19-1.17 8.25Zm-.08-10.8a1 1 0 0 1-.27-.69 1.24 1.24 0 0 1 .34-.89 1.07 1.07 0 0 1 .82-.37.94.94 0 0 1 .7.27.93.93 0 0 1 .26.66 1.35 1.35 0 0 1-.33.92 1.14 1.14 0 0 1-.88.38.9.9 0 0 1-.64-.28ZM315.15 38.24a4.26 4.26 0 0 1-2.23.6 3.45 3.45 0 0 1-2-.53 3.23 3.23 0 0 1-1.15-1.41 4.83 4.83 0 0 1-.36-1.87 7.38 7.38 0 0 1 .67-3.14 5.91 5.91 0 0 1 1.92-2.33 4.33 4.33 0 0 1 2.62-.88 2.64 2.64 0 0 1 1.88.6 2.06 2.06 0 0 1 .63 1.56 2.66 2.66 0 0 1-1 2.11 6.62 6.62 0 0 1-2.37 1.28 9.48 9.48 0 0 1-2.46.45 3.85 3.85 0 0 0 .42 2.13 1.68 1.68 0 0 0 1.6.91 3.61 3.61 0 0 0 1.54-.36 4.41 4.41 0 0 0 1.39-1l.38.65a4.39 4.39 0 0 1-1.48 1.23Zm-2.41-8a4.82 4.82 0 0 0-1 1.65 7.41 7.41 0 0 0-.44 1.94 5.85 5.85 0 0 0 1.86-.39 4.34 4.34 0 0 0 1.6-1 2 2 0 0 0 .65-1.46 1.5 1.5 0 0 0-.33-1.05 1.14 1.14 0 0 0-.88-.35 2 2 0 0 0-1.46.67ZM323.42 29.32a3.62 3.62 0 0 1 2-.64 1.89 1.89 0 0 1 1.51.6 2.93 2.93 0 0 1 .53 1.95 16.77 16.77 0 0 1-.39 2.68l-.07.4-.14.85a12.6 12.6 0 0 0-.28 2.12c0 .32.08.47.23.47a1.35 1.35 0 0 0 .82-.44l.21.46a1.7 1.7 0 0 1-.36.4 2.81 2.81 0 0 1-.7.45 1.92 1.92 0 0 1-.9.2c-.74 0-1.11-.35-1.11-1.07a14.6 14.6 0 0 1 .32-2.14l.16-.84.07-.42c.11-.63.21-1.18.28-1.66a9 9 0 0 0 .1-1.32 2 2 0 0 0-.23-1.12 1 1 0 0 0-.84-.3 2.63 2.63 0 0 0-1.57.69 6.6 6.6 0 0 0-1.48 1.67l-.86 6.34H319l1.13-8.49-.86-.42.14-.67 2.14-.39.37.2-.23 2.1a6.56 6.56 0 0 1 1.73-1.66ZM334.3 29.79a2.22 2.22 0 0 0-1.53.62 4.14 4.14 0 0 0-1 1.74 7.68 7.68 0 0 0-.38 2.55 4.11 4.11 0 0 0 .49 2.24 1.61 1.61 0 0 0 1.42.74 2.78 2.78 0 0 0 1.26-.27 5.52 5.52 0 0 0 1.14-.81l.36.64a4.56 4.56 0 0 1-1.31 1.08 3.85 3.85 0 0 1-2 .5 2.79 2.79 0 0 1-2.31-1 4.57 4.57 0 0 1-.83-2.9 7.19 7.19 0 0 1 .61-2.87 5.94 5.94 0 0 1 1.77-2.38 4.24 4.24 0 0 1 2.76-.95 5.7 5.7 0 0 1 1.06.11 3.2 3.2 0 0 1 .92.3l-.47 1.7-.3-.11a2.91 2.91 0 0 0-1.66-.93ZM343.32 38.24a4.26 4.26 0 0 1-2.23.6 3.42 3.42 0 0 1-1.95-.53A3.17 3.17 0 0 1 338 36.9a4.66 4.66 0 0 1-.37-1.87 7.53 7.53 0 0 1 .67-3.14 6 6 0 0 1 1.86-2.33 4.36 4.36 0 0 1 2.63-.88 2.65 2.65 0 0 1 1.88.6 2.06 2.06 0 0 1 .63 1.56 2.69 2.69 0 0 1-1 2.11 6.66 6.66 0 0 1-2.38 1.28 9.33 9.33 0 0 1-2.46.45 4 4 0 0 0 .42 2.13 1.68 1.68 0 0 0 1.6.91 3.65 3.65 0 0 0 1.55-.36 4.37 4.37 0 0 0 1.38-1l.39.65a4.43 4.43 0 0 1-1.48 1.23Zm-2.4-8a4.67 4.67 0 0 0-1 1.65 7 7 0 0 0-.44 1.94 5.79 5.79 0 0 0 1.85-.39 4.25 4.25 0 0 0 1.6-1 2 2 0 0 0 .65-1.46 1.5 1.5 0 0 0-.32-1.05 1.17 1.17 0 0 0-.89-.35 1.93 1.93 0 0 0-1.45.67ZM351.91 29.91a3.08 3.08 0 0 0-1.24-.24 2.15 2.15 0 0 0-1.3.35 1.18 1.18 0 0 0-.49 1 1.54 1.54 0 0 0 .4 1.06 6.17 6.17 0 0 0 1.13 1c.42.33.76.61 1 .85a3.35 3.35 0 0 1 .67.87 2.38 2.38 0 0 1 .3 1.2 2.4 2.4 0 0 1-1 2.07 4.21 4.21 0 0 1-2.53.73 7.55 7.55 0 0 1-1.57-.17 2.73 2.73 0 0 1-1-.39l.29-1.21a3.77 3.77 0 0 0 1 .5 3.94 3.94 0 0 0 1.36.24 2.47 2.47 0 0 0 1.31-.33 1.14 1.14 0 0 0 .55-1.06 1.58 1.58 0 0 0-.43-1.09 8 8 0 0 0-1.26-1 3.53 3.53 0 0 1-1.81-2.86 2.43 2.43 0 0 1 .46-1.45 2.92 2.92 0 0 1 1.25-1 4.48 4.48 0 0 1 1.75-.34 7.2 7.2 0 0 1 1.29.12 4.56 4.56 0 0 1 .92.22l-.3 1.33a1.83 1.83 0 0 0-.75-.4ZM287 50.81h8.32l-.12 2.79h-1l-.28-1.84-4-.14-.67 5 4.07-.14-.12 1.32-4-.14-.81 5.34 4.95-.21 1-2.12 1 .19-.71 3h-9.33l.07-.68 1.32-.21 1.4-11.19-1.19-.2ZM301.65 54.52a3.52 3.52 0 0 1 2-.64 1.89 1.89 0 0 1 1.51.6 2.89 2.89 0 0 1 .53 1.94 16.85 16.85 0 0 1-.39 2.69l-.07.4-.14.84a12.68 12.68 0 0 0-.28 2.13c0 .31.07.47.23.47a1.41 1.41 0 0 0 .82-.44l.14.49a1.76 1.76 0 0 1-.37.4 3.17 3.17 0 0 1-.69.45 2 2 0 0 1-.9.2A1 1 0 0 1 303 63a14.6 14.6 0 0 1 .32-2.14l.16-.84.07-.42c.11-.64.21-1.19.28-1.66a9.18 9.18 0 0 0 .1-1.33 2 2 0 0 0-.23-1.11 1 1 0 0 0-.84-.31 2.59 2.59 0 0 0-1.57.7 6.6 6.6 0 0 0-1.48 1.67l-.86 6.33h-1.67l1.13-8.49-.86-.42.14-.66 2.14-.39.37.19-.23 2.11a6.56 6.56 0 0 1 1.68-1.71ZM313.74 66.64a4.23 4.23 0 0 1-1.77 1.2 5.86 5.86 0 0 1-2 .37 7.37 7.37 0 0 1-1.13-.09 4.89 4.89 0 0 1-.87-.22l.37-1.42a6.44 6.44 0 0 0 1 .39 4.29 4.29 0 0 0 1.22.18 2.62 2.62 0 0 0 1.66-.43 2.58 2.58 0 0 0 .71-1.62l.33-2.33a4.25 4.25 0 0 1-1.18 1 3 3 0 0 1-1.52.39 2.52 2.52 0 0 1-2.17-1 4.5 4.5 0 0 1-.72-2.68 7.33 7.33 0 0 1 .66-3 6.45 6.45 0 0 1 1.95-2.49 4.73 4.73 0 0 1 3-1 5.1 5.1 0 0 1 1 .11 5.19 5.19 0 0 1 .91.28l1.09-.39-1.58 10.63a3.73 3.73 0 0 1-.96 2.12ZM313 54.81a2.66 2.66 0 0 0-2 .85 5.43 5.43 0 0 0-1.22 2.11 7.91 7.91 0 0 0-.4 2.46 3.81 3.81 0 0 0 .42 2 1.31 1.31 0 0 0 1.17.71 2.42 2.42 0 0 0 1.37-.44 3.83 3.83 0 0 0 1-1l.93-6.28a2.13 2.13 0 0 0-1.27-.41ZM320.16 62.51a.56.56 0 0 0 .08.32.24.24 0 0 0 .2.12.8.8 0 0 0 .4-.12 4.16 4.16 0 0 0 .5-.41l.23.42a3.57 3.57 0 0 1-.78.78 2 2 0 0 1-1.24.4 1.32 1.32 0 0 1-.89-.27.92.92 0 0 1-.25-.82c0-.29.18-1.43.46-3.4.16-1.07.36-2.48.59-4.23l-1.09-.4.11-.6 2.49-.4.39.19-1.18 8.25Zm-.08-10.81a.93.93 0 0 1-.27-.68 1.25 1.25 0 0 1 .35-.89 1 1 0 0 1 .81-.37.93.93 0 0 1 .7.27.9.9 0 0 1 .27.66 1.36 1.36 0 0 1-.34.92 1.11 1.11 0 0 1-.88.37.87.87 0 0 1-.64-.28ZM328.56 54.52a3.54 3.54 0 0 1 2-.64 1.89 1.89 0 0 1 1.51.6 2.89 2.89 0 0 1 .53 1.94 16.85 16.85 0 0 1-.39 2.69l-.07.4-.14.84a12.68 12.68 0 0 0-.28 2.13c0 .31.08.47.23.47a1.41 1.41 0 0 0 .82-.44l.23.49a1.76 1.76 0 0 1-.37.4 3.17 3.17 0 0 1-.69.45 2 2 0 0 1-.9.2 1 1 0 0 1-1.16-1.05 14.6 14.6 0 0 1 .32-2.14l.16-.84.07-.42c.11-.64.21-1.19.28-1.66a9.18 9.18 0 0 0 .1-1.33 2 2 0 0 0-.23-1.11 1 1 0 0 0-.84-.31 2.59 2.59 0 0 0-1.57.7 6.6 6.6 0 0 0-1.48 1.67l-.86 6.33h-1.67l1.13-8.49-.86-.42.14-.66 2.14-.39.37.19-.23 2.11a6.56 6.56 0 0 1 1.71-1.71ZM340.41 63.44a4.26 4.26 0 0 1-2.23.6 3.35 3.35 0 0 1-1.95-.54 3 3 0 0 1-1.15-1.4 4.66 4.66 0 0 1-.37-1.87 7.38 7.38 0 0 1 .67-3.14 5.91 5.91 0 0 1 1.86-2.33 4.29 4.29 0 0 1 2.62-.88 2.62 2.62 0 0 1 1.88.6 2 2 0 0 1 .63 1.56 2.63 2.63 0 0 1-1 2.1 6.47 6.47 0 0 1-2.37 1.28 9.38 9.38 0 0 1-2.46.46A4 4 0 0 0 337 62a1.69 1.69 0 0 0 1.6.9 3.61 3.61 0 0 0 1.54-.36 4.27 4.27 0 0 0 1.39-1l.39.65a4.68 4.68 0 0 1-1.51 1.25Zm-2.4-8a4.53 4.53 0 0 0-1 1.65 6.69 6.69 0 0 0-.44 1.94 6.13 6.13 0 0 0 1.85-.39 4.25 4.25 0 0 0 1.6-1 2 2 0 0 0 .65-1.46 1.55 1.55 0 0 0-.32-1.05 1.14 1.14 0 0 0-.89-.36 2 2 0 0 0-1.46.68ZM349.39 63.44a4.26 4.26 0 0 1-2.23.6 3.35 3.35 0 0 1-2-.54 3.09 3.09 0 0 1-1.15-1.4 4.66 4.66 0 0 1-.37-1.87 7.38 7.38 0 0 1 .68-3.14 5.91 5.91 0 0 1 1.86-2.33 4.25 4.25 0 0 1 2.62-.88 2.65 2.65 0 0 1 1.88.6 2 2 0 0 1 .63 1.56 2.66 2.66 0 0 1-1 2.1 6.51 6.51 0 0 1-2.31 1.28 9.38 9.38 0 0 1-2.46.46 3.94 3.94 0 0 0 .43 2.13 1.66 1.66 0 0 0 1.59.9 3.65 3.65 0 0 0 1.55-.36 4.34 4.34 0 0 0 1.38-1l.39.65a4.68 4.68 0 0 1-1.49 1.24Zm-2.4-8a4.67 4.67 0 0 0-1 1.65 7 7 0 0 0-.44 1.94 6.07 6.07 0 0 0 1.85-.39 4.38 4.38 0 0 0 1.61-1 2 2 0 0 0 .65-1.46 1.5 1.5 0 0 0-.33-1.05 1.14 1.14 0 0 0-.89-.36 2 2 0 0 0-1.44.68ZM356.34 55.24a4.21 4.21 0 0 1 1.13-1 2.81 2.81 0 0 1 1.4-.38.93.93 0 0 1 .56.12l-.37 1.86a1.64 1.64 0 0 0-.86-.18 2.68 2.68 0 0 0-1.48.5 3.31 3.31 0 0 0-1.14 1.4l-.8 6.24h-1.69l1.11-8.45-.88-.44.12-.65 2.07-.4.35.21-.12 1.56-.08.7a3.9 3.9 0 0 1 .68-1.09ZM362.32 62.51a.56.56 0 0 0 .08.32.23.23 0 0 0 .2.12.8.8 0 0 0 .4-.12 4.16 4.16 0 0 0 .5-.41l.22.42a3.18 3.18 0 0 1-.78.78 2 2 0 0 1-1.23.4 1.3 1.3 0 0 1-.89-.27.92.92 0 0 1-.25-.82c0-.29.17-1.43.45-3.4.17-1.07.36-2.48.6-4.23l-1.09-.4.11-.6 2.49-.4.38.19-1.17 8.25Zm-.08-10.81a.93.93 0 0 1-.24-.7 1.24 1.24 0 0 1 .34-.89 1.07 1.07 0 0 1 .82-.37.94.94 0 0 1 .7.27.93.93 0 0 1 .26.66 1.35 1.35 0 0 1-.33.92 1.12 1.12 0 0 1-.88.37.86.86 0 0 1-.67-.26ZM370.36 54.52a3.55 3.55 0 0 1 2-.64 1.91 1.91 0 0 1 1.51.6 2.89 2.89 0 0 1 .52 1.94 17.7 17.7 0 0 1-.38 2.69l-.07.4-.14.84a12.68 12.68 0 0 0-.28 2.13c0 .31.07.47.22.47a1.4 1.4 0 0 0 .83-.44l.21.46a1.76 1.76 0 0 1-.37.4 3.74 3.74 0 0 1-.69.45 2.13 2.13 0 0 1-.91.2 1 1 0 0 1-1.1-1.07 14.1 14.1 0 0 1 .31-2.14l.16-.84.07-.42c.12-.64.21-1.19.28-1.66a9.27 9.27 0 0 0 .11-1.33 1.88 1.88 0 0 0-.24-1.11 1 1 0 0 0-.83-.31 2.59 2.59 0 0 0-1.57.7 6.6 6.6 0 0 0-1.48 1.67l-.86 6.33H366l1.12-8.49-.86-.42.14-.66 2.14-.39.37.19-.23 2.11a6.72 6.72 0 0 1 1.68-1.66ZM382.46 66.64a4.23 4.23 0 0 1-1.77 1.2 5.87 5.87 0 0 1-2 .37 7.34 7.34 0 0 1-1.12-.09 4.82 4.82 0 0 1-.88-.22l.37-1.42a6.58 6.58 0 0 0 1 .39 4.24 4.24 0 0 0 1.22.18 2.57 2.57 0 0 0 1.65-.43 2.53 2.53 0 0 0 .72-1.62l.33-2.33a4.25 4.25 0 0 1-1.18 1 3.07 3.07 0 0 1-1.52.39 2.52 2.52 0 0 1-2.17-1 4.5 4.5 0 0 1-.73-2.68 7.35 7.35 0 0 1 .67-3 6.27 6.27 0 0 1 1.95-2.51 4.71 4.71 0 0 1 3-1 5.1 5.1 0 0 1 1 .11 5.47 5.47 0 0 1 .91.28l1.09-.39-1.58 10.63a3.86 3.86 0 0 1-.96 2.14Zm-.7-11.83a2.62 2.62 0 0 0-2 .85 5.31 5.31 0 0 0-1.22 2.11 7.93 7.93 0 0 0-.41 2.46 3.7 3.7 0 0 0 .43 2 1.31 1.31 0 0 0 1.17.71 2.42 2.42 0 0 0 1.37-.44 3.79 3.79 0 0 0 1-1l.93-6.28a2.08 2.08 0 0 0-1.27-.41ZM295.85 80.3q1.44-3.12 1.89-4.29h3.76l-.07.75-1.56.19-.34 11.2 1.49.21-.02.64h-4.82l.07-.68 1.6-.21.4-7.76.23-3.56L297.1 80l-4.1 9.08-.94.12-1.44-9-.55-3.33-.71 3.4-1.88 7.9 1.77.21-.07.68h-4.53l.07-.68 1.46-.21L289 77l-1.62-.19.11-.75h4.07l1.35 8.56.23 1.79.77-1.76q.49-1.22 1.94-4.35ZM308 88.64a4.35 4.35 0 0 1-2.23.59 3.38 3.38 0 0 1-2-.53 3.26 3.26 0 0 1-1.15-1.4 4.87 4.87 0 0 1-.36-1.87 7.34 7.34 0 0 1 .67-3.14 6 6 0 0 1 1.91-2.29 4.32 4.32 0 0 1 2.62-.87 2.63 2.63 0 0 1 1.88.59 2.06 2.06 0 0 1 .63 1.56 2.65 2.65 0 0 1-1 2.11 6.62 6.62 0 0 1-2.37 1.28 10 10 0 0 1-2.46.46 3.89 3.89 0 0 0 .42 2.13 1.69 1.69 0 0 0 1.6.9 3.61 3.61 0 0 0 1.54-.36 4.3 4.3 0 0 0 1.39-1l.38.65a4.52 4.52 0 0 1-1.47 1.19Zm-2.41-8a4.68 4.68 0 0 0-1 1.64 7.5 7.5 0 0 0-.44 1.94 6.11 6.11 0 0 0 1.86-.38 4.61 4.61 0 0 0 1.6-1 2 2 0 0 0 .65-1.47 1.54 1.54 0 0 0-.32-1 1.15 1.15 0 0 0-.89-.36 2 2 0 0 0-1.45.64ZM318.78 87.71c0 .29.09.44.26.44a1.42 1.42 0 0 0 .81-.44l.24.44a3.31 3.31 0 0 1-.76.71 1.9 1.9 0 0 1-1.15.36c-.69 0-1-.38-1-1.13v-.38a4.57 4.57 0 0 1-1.23 1.07 3.18 3.18 0 0 1-1.65.44 2.46 2.46 0 0 1-2.14-1 4.54 4.54 0 0 1-.72-2.68 7.24 7.24 0 0 1 .67-3 6.3 6.3 0 0 1 1.89-2.48 4.67 4.67 0 0 1 3-1 4.42 4.42 0 0 1 1.31.21l.48-3.16-1.16-.3.14-.61 2.47-.32.39.23-1.83 12.4a.59.59 0 0 0-.02.2Zm-2-7.7a2.62 2.62 0 0 0-2 .85 5.14 5.14 0 0 0-1.21 2.1 8 8 0 0 0-.4 2.47 3.83 3.83 0 0 0 .42 2 1.27 1.27 0 0 0 1.16.7 2.39 2.39 0 0 0 1.4-.46 3.7 3.7 0 0 0 1-1l.95-6.19a2.2 2.2 0 0 0-1.32-.48ZM324.44 87.71a.56.56 0 0 0 .08.32.25.25 0 0 0 .21.12.79.79 0 0 0 .39-.13 3.18 3.18 0 0 0 .5-.4l.23.42a3.35 3.35 0 0 1-.78.77 2 2 0 0 1-1.24.41 1.34 1.34 0 0 1-.89-.28.92.92 0 0 1-.25-.81c0-.29.18-1.43.46-3.41.16-1.06.36-2.47.59-4.22l-1.08-.41.1-.59 2.49-.41.39.2-1.18 8.24Zm-.07-10.81a1 1 0 0 1-.28-.68 1.29 1.29 0 0 1 .35-.9 1.1 1.1 0 0 1 .81-.37.92.92 0 0 1 1 .93 1.29 1.29 0 0 1-.34.92 1.11 1.11 0 0 1-.87.38.84.84 0 0 1-.67-.28ZM332.76 80.18a2.22 2.22 0 0 0-1.53.62 4.15 4.15 0 0 0-1.06 1.74 8 8 0 0 0-.37 2.55 4.09 4.09 0 0 0 .49 2.24 1.59 1.59 0 0 0 1.42.75 2.71 2.71 0 0 0 1.29-.28 5.56 5.56 0 0 0 1.15-.81l.35.65a4.84 4.84 0 0 1-1.3 1.08 3.94 3.94 0 0 1-2 .5 2.78 2.78 0 0 1-2.31-1 4.49 4.49 0 0 1-.83-2.9 7.35 7.35 0 0 1 .6-2.87 6.1 6.1 0 0 1 1.72-2.45 4.26 4.26 0 0 1 2.77-.94 5.66 5.66 0 0 1 1.06.1 3.31 3.31 0 0 1 .92.3l-.47 1.7-.3-.1a2.88 2.88 0 0 0-1.6-.88ZM338.88 87.71a.56.56 0 0 0 .12.29.23.23 0 0 0 .2.12.82.82 0 0 0 .4-.13 3.18 3.18 0 0 0 .5-.4l.23.42a3.56 3.56 0 0 1-.78.77 2 2 0 0 1-1.24.41 1.32 1.32 0 0 1-.89-.28.9.9 0 0 1-.25-.81c0-.29.18-1.43.46-3.41.16-1.06.36-2.47.59-4.22l-1.09-.41.11-.59 2.49-.41.39.2-1.18 8.24Zm-.08-10.81a1 1 0 0 1-.27-.68 1.29 1.29 0 0 1 .35-.9 1.07 1.07 0 0 1 .81-.37.92.92 0 0 1 1 .93 1.34 1.34 0 0 1-.34.92 1.11 1.11 0 0 1-.88.38.87.87 0 0 1-.67-.28ZM347.19 79.72a3.54 3.54 0 0 1 2-.64 1.89 1.89 0 0 1 1.51.59 2.93 2.93 0 0 1 .53 2 16.77 16.77 0 0 1-.39 2.68l-.07.41-.14.84a12.6 12.6 0 0 0-.28 2.12c0 .32.08.48.23.48a1.38 1.38 0 0 0 .82-.44l.21.45a1.91 1.91 0 0 1-.36.41 3.11 3.11 0 0 1-.7.44 1.93 1.93 0 0 1-.9.21 1 1 0 0 1-1.11-1.07 14.24 14.24 0 0 1 .32-2.14l.16-.85.07-.42c.11-.63.21-1.18.28-1.66a9 9 0 0 0 .1-1.32 1.87 1.87 0 0 0-.23-1.11 1 1 0 0 0-.84-.31 2.66 2.66 0 0 0-1.57.69 6.48 6.48 0 0 0-1.48 1.68l-.89 6.24h-1.66l1.12-8.49-.86-.42.14-.67 2.14-.38.37.19-.23 2.1a6.52 6.52 0 0 1 1.71-1.61ZM359 88.64a4.35 4.35 0 0 1-2.23.59 3.34 3.34 0 0 1-1.95-.53 3.19 3.19 0 0 1-1.15-1.4 4.69 4.69 0 0 1-.37-1.87 7.34 7.34 0 0 1 .67-3.14 6 6 0 0 1 1.9-2.29 4.35 4.35 0 0 1 2.63-.87 2.61 2.61 0 0 1 1.87.59 2 2 0 0 1 .64 1.56 2.68 2.68 0 0 1-1 2.11 6.75 6.75 0 0 1-2.38 1.28 9.81 9.81 0 0 1-2.46.46 4.08 4.08 0 0 0 .42 2.13 1.69 1.69 0 0 0 1.6.9 3.65 3.65 0 0 0 1.55-.36 4.37 4.37 0 0 0 1.38-1l.39.65a4.57 4.57 0 0 1-1.51 1.19Zm-2.4-8a4.54 4.54 0 0 0-1 1.64 6.76 6.76 0 0 0-.44 1.94 6 6 0 0 0 1.85-.38 4.52 4.52 0 0 0 1.6-1 2 2 0 0 0 .65-1.47 1.49 1.49 0 0 0-.32-1 1.14 1.14 0 0 0-.89-.36 2 2 0 0 0-1.41.64Z" class="cls-2" transform="translate(-24.97 -24.05)"/> </svg> </a></div> <div class="global-nav__controls"><button class="controls__search" style="display: none;"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class=""><path d="M13.8 21.6a7.8 7.8 0 110-15.6 7.8 7.8 0 010 15.6zm0-2a5.8 5.8 0 100-11.6 5.8 5.8 0 000 11.6z"></path><path d="M17.899 19.325l1.414-1.414 4.322 4.322-1.414 1.414z"></path></svg></button> <button class="controls__close" onclick="toggleSearch()"><span class="menus__close-label"> Close </span> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class=""><path fill-rule="evenodd" d="M20.728 8l1.818 1.818-5.455 5.455 5.455 5.455-1.818 1.818-5.455-5.455-5.455 5.455L8 20.728l5.455-5.455L8 9.818 9.818 8l5.455 5.455z"></path></svg></button></div></div> <div class="mega-menu__content"> <div class="search-form sf-top" > <div class="search-form__container"> <label for="inputsearch"> Search for Publications Only </label> <form id="searchFormNAP" action="/search" enctype="application/x-www-form-urlencoded"> <input id="inputsearch" name="term" type="text" placeholder="Type a title, topic, ISBN, or DOI and hit enter"> <input type="hidden" name="v:project" value="uweb_proj_ext"> <button class="search-form__submit"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class=""> <path d="M13.8 21.6a7.8 7.8 0 110-15.6 7.8 7.8 0 010 15.6zm0-2a5.8 5.8 0 100-11.6 5.8 5.8 0 000 11.6z"></path> <path d="M17.899 19.325l1.414-1.414 4.322 4.322-1.414 1.414z"></path> </svg> </button> </form> </div> </div> <div class="search-form"> <div class="search-form__container"> <label for="globalSearch"> Search All</label> <form id="searchForm" action="https://sparck.nationalacademies.org/vivisimo/cgi-bin/query-meta" enctype="application/x-www-form-urlencoded"> <input id="globalSearch" name="query" type="text" placeholder="Type anything and hit enter"> <input type="hidden" name="v:project" value="uweb_proj_ext"> <button class="search-form__submit"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class=""> <path d="M13.8 21.6a7.8 7.8 0 110-15.6 7.8 7.8 0 010 15.6zm0-2a5.8 5.8 0 100-11.6 5.8 5.8 0 000 11.6z"></path> <path d="M17.899 19.325l1.414-1.414 4.322 4.322-1.414 1.414z"></path> </svg> </button> </form> </div> </div> </div> </div> <div tabindex="0" aria-hidden="true"></div> </div>   <div aria-hidden="true" class="mega-menu" id="mobile-menu" style="display: none;"> <div data-lock=""> <div class="mega-menu__header"> <div class="global-nav__logo" style="padding-left: 10px;"> <a class="navbar-brand js-scroll-trigger" href="https://www.nationalacademies.org/"> <svg xmlns="http://www.w3.org/2000/svg" id="nasemLogo" data-name="nasemLogo" viewBox="0 0 360 66.64"> <defs/> <path d="m4.26 8.63 19.56 20.49V1.72h-3.47v18.93L.8.16v27.32h3.46V8.63zM32.55 27.48h3.83l8.15-19.2 7.93 18.99.09.21h3.82L44.62 0 32.55 27.48zM175.05 27.48h3.83l8.16-19.2 7.93 18.99.08.21h3.83L187.12 0l-12.07 27.48zM68.23 27.48h3.47V5.03h7.72V1.72H60.51v3.31h7.72v22.45zM90.08 1.72h3.46v25.76h-3.46z" class="cls-2"/> <path d="M157.14 38.67A13.39 13.39 0 1 0 143.75 52a13.21 13.21 0 0 0 13.39-13.33Zm-3.54 0a9.85 9.85 0 1 1-9.85-10 9.93 9.93 0 0 1 9.85 10Z" class="cls-2" transform="translate(-24.97 -24.05)"/> <path d="m146.56 8.63 19.56 20.49V1.72h-3.47v18.93L143.1.16v27.32h3.46V8.63zM210.95 1.72h-3.46v25.76h13.8v-3.31h-10.34V1.72z" class="cls-2"/> <path d="M67.41 63A13.13 13.13 0 0 0 54 76.37a13 13 0 0 0 13.26 13.24A13.48 13.48 0 0 0 75 87.1l.14-.1v-4.46l-.58.58a10.91 10.91 0 0 1-2.81 2 10 10 0 0 1-4.51 1.13c-6.74 0-9.77-5.78-9.77-9.89a9.82 9.82 0 0 1 9.74-10.11 10.44 10.44 0 0 1 4.18.94 12 12 0 0 1 3.17 2.27l.58.58v-4.41l-.13-.1a12.1 12.1 0 0 0-7.6-2.53ZM130 66.4a14 14 0 0 0-9.47-3h-5.45v25.75h5.42c4.25 0 6.88-.83 9.39-3a12.32 12.32 0 0 0 4.52-9.89A12.54 12.54 0 0 0 130 66.4Zm-2.39 17.26a10.37 10.37 0 0 1-7 2.18h-2.11V66.7h2.11c6.21 0 10.22 3.77 10.22 9.59a9.23 9.23 0 0 1-3.25 7.37Z" class="cls-2" transform="translate(-24.97 -24.05)"/> <path d="M119.94 65.11h15.33V61.8h-11.86v-9.07h10.38v-3.31h-10.38v-6.76h11.86v-3.32h-15.33v25.77zM201.26 65.11h15.33V61.8h-11.86v-9.07h10.37v-3.31h-10.37v-6.76h11.86v-3.32h-15.33v25.77zM158.66 58.65l-9.79-21.53-4.42 27.99h3.56l2.36-16.59 8.25 18.12 8.35-18.12 2.25 16.59h3.56l-4.14-28.03-9.98 21.57zM184.29 39.34h3.46V65.1h-3.46z" class="cls-2"/> <path d="M263.7 76.76a12.7 12.7 0 0 0-4-2.44l-2.42-1a8 8 0 0 1-2.53-1.51 2.32 2.32 0 0 1-.83-1.94c0-2.11 1.56-3.53 3.87-3.53a4.18 4.18 0 0 1 2.61.79 5.51 5.51 0 0 1 1.37 1.77l.17.34 2.8-1.85-.14-.27a7.79 7.79 0 0 0-2.56-2.91 7.16 7.16 0 0 0-4.18-1.21c-4.34 0-7.37 2.8-7.37 6.8a5.53 5.53 0 0 0 1.83 4.35 10.74 10.74 0 0 0 3.24 2l2.44 1.17a10.81 10.81 0 0 1 2.94 1.68 3.39 3.39 0 0 1 1.13 2.68A4.8 4.8 0 0 1 254 85a5.6 5.6 0 0 1-1.42-3l-.05-.39-3.4.94.07.32a9.51 9.51 0 0 0 2.43 4.61 7.73 7.73 0 0 0 5.69 2.13 7.9 7.9 0 0 0 8.28-8 6.38 6.38 0 0 0-1.9-4.85Z" class="cls-2" transform="translate(-24.97 -24.05)"/> <path d="M0 65.11h3.83l8.16-19.21 7.92 19 .09.21h3.83L12.07 37.63 0 65.11zM57.37 65.11h3.83l8.15-19.21 7.93 19 .08.21h3.83L69.44 37.63 57.37 65.11z" class="cls-2"/> <path d="M292 26.45a3.91 3.91 0 0 0-1.07-.14 2.94 2.94 0 0 0-1.74.52 1.71 1.71 0 0 0-.72 1.47 2.36 2.36 0 0 0 .63 1.7 9.45 9.45 0 0 0 1.9 1.38 15.52 15.52 0 0 1 1.45 1 4.28 4.28 0 0 1 .94 1.12 2.87 2.87 0 0 1 .38 1.51 3.57 3.57 0 0 1-.57 2 3.79 3.79 0 0 1-1.6 1.34 5.79 5.79 0 0 1-2.39.47 9.63 9.63 0 0 1-2.22-.25 4.15 4.15 0 0 1-1.41-.52l.39-2.49H287l.11 1.84a2.93 2.93 0 0 0 .92.39 5 5 0 0 0 1.16.14 3.39 3.39 0 0 0 2-.6 1.94 1.94 0 0 0 .83-1.68 2.25 2.25 0 0 0-.56-1.54 7.66 7.66 0 0 0-1.7-1.32c-.6-.39-1.1-.75-1.51-1.07a4.43 4.43 0 0 1-1-1.2 2.94 2.94 0 0 1-.43-1.59 3.08 3.08 0 0 1 .57-1.85 3.58 3.58 0 0 1 1.55-1.23 5.17 5.17 0 0 1 2.13-.43 7.84 7.84 0 0 1 2 .21 4 4 0 0 1 1.25.51l-.4 2.31h-.95l-.14-1.68a2.39 2.39 0 0 0-.83-.32ZM300.27 29.79a2.2 2.2 0 0 0-1.53.62 4.15 4.15 0 0 0-1.06 1.74 8 8 0 0 0-.38 2.55 4.11 4.11 0 0 0 .5 2.24 1.6 1.6 0 0 0 1.42.74 2.71 2.71 0 0 0 1.25-.27 5.56 5.56 0 0 0 1.15-.81l.35.64a4.42 4.42 0 0 1-1.31 1.08 3.78 3.78 0 0 1-2 .5 2.76 2.76 0 0 1-2.31-1 4.51 4.51 0 0 1-.83-2.9 7.35 7.35 0 0 1 .6-2.87 6 6 0 0 1 1.77-2.38 4.27 4.27 0 0 1 2.77-.95 5.7 5.7 0 0 1 1.06.11 3.31 3.31 0 0 1 .92.3l-.48 1.7-.29-.11a2.91 2.91 0 0 0-1.6-.93ZM306.13 37.31a.54.54 0 0 0 .08.33.22.22 0 0 0 .2.11.74.74 0 0 0 .39-.12 2.88 2.88 0 0 0 .5-.4l.23.42a3.34 3.34 0 0 1-.78.77 2 2 0 0 1-1.23.4 1.3 1.3 0 0 1-.89-.27.9.9 0 0 1-.26-.81c0-.3.18-1.43.46-3.41q.24-1.59.6-4.23l-1.09-.4.11-.6 2.49-.4.38.19-1.17 8.25Zm-.08-10.8a1 1 0 0 1-.27-.69 1.24 1.24 0 0 1 .34-.89 1.07 1.07 0 0 1 .82-.37.94.94 0 0 1 .7.27.93.93 0 0 1 .26.66 1.35 1.35 0 0 1-.33.92 1.14 1.14 0 0 1-.88.38.9.9 0 0 1-.64-.28ZM315.15 38.24a4.26 4.26 0 0 1-2.23.6 3.45 3.45 0 0 1-2-.53 3.23 3.23 0 0 1-1.15-1.41 4.83 4.83 0 0 1-.36-1.87 7.38 7.38 0 0 1 .67-3.14 5.91 5.91 0 0 1 1.92-2.33 4.33 4.33 0 0 1 2.62-.88 2.64 2.64 0 0 1 1.88.6 2.06 2.06 0 0 1 .63 1.56 2.66 2.66 0 0 1-1 2.11 6.62 6.62 0 0 1-2.37 1.28 9.48 9.48 0 0 1-2.46.45 3.85 3.85 0 0 0 .42 2.13 1.68 1.68 0 0 0 1.6.91 3.61 3.61 0 0 0 1.54-.36 4.41 4.41 0 0 0 1.39-1l.38.65a4.39 4.39 0 0 1-1.48 1.23Zm-2.41-8a4.82 4.82 0 0 0-1 1.65 7.41 7.41 0 0 0-.44 1.94 5.85 5.85 0 0 0 1.86-.39 4.34 4.34 0 0 0 1.6-1 2 2 0 0 0 .65-1.46 1.5 1.5 0 0 0-.33-1.05 1.14 1.14 0 0 0-.88-.35 2 2 0 0 0-1.46.67ZM323.42 29.32a3.62 3.62 0 0 1 2-.64 1.89 1.89 0 0 1 1.51.6 2.93 2.93 0 0 1 .53 1.95 16.77 16.77 0 0 1-.39 2.68l-.07.4-.14.85a12.6 12.6 0 0 0-.28 2.12c0 .32.08.47.23.47a1.35 1.35 0 0 0 .82-.44l.21.46a1.7 1.7 0 0 1-.36.4 2.81 2.81 0 0 1-.7.45 1.92 1.92 0 0 1-.9.2c-.74 0-1.11-.35-1.11-1.07a14.6 14.6 0 0 1 .32-2.14l.16-.84.07-.42c.11-.63.21-1.18.28-1.66a9 9 0 0 0 .1-1.32 2 2 0 0 0-.23-1.12 1 1 0 0 0-.84-.3 2.63 2.63 0 0 0-1.57.69 6.6 6.6 0 0 0-1.48 1.67l-.86 6.34H319l1.13-8.49-.86-.42.14-.67 2.14-.39.37.2-.23 2.1a6.56 6.56 0 0 1 1.73-1.66ZM334.3 29.79a2.22 2.22 0 0 0-1.53.62 4.14 4.14 0 0 0-1 1.74 7.68 7.68 0 0 0-.38 2.55 4.11 4.11 0 0 0 .49 2.24 1.61 1.61 0 0 0 1.42.74 2.78 2.78 0 0 0 1.26-.27 5.52 5.52 0 0 0 1.14-.81l.36.64a4.56 4.56 0 0 1-1.31 1.08 3.85 3.85 0 0 1-2 .5 2.79 2.79 0 0 1-2.31-1 4.57 4.57 0 0 1-.83-2.9 7.19 7.19 0 0 1 .61-2.87 5.94 5.94 0 0 1 1.77-2.38 4.24 4.24 0 0 1 2.76-.95 5.7 5.7 0 0 1 1.06.11 3.2 3.2 0 0 1 .92.3l-.47 1.7-.3-.11a2.91 2.91 0 0 0-1.66-.93ZM343.32 38.24a4.26 4.26 0 0 1-2.23.6 3.42 3.42 0 0 1-1.95-.53A3.17 3.17 0 0 1 338 36.9a4.66 4.66 0 0 1-.37-1.87 7.53 7.53 0 0 1 .67-3.14 6 6 0 0 1 1.86-2.33 4.36 4.36 0 0 1 2.63-.88 2.65 2.65 0 0 1 1.88.6 2.06 2.06 0 0 1 .63 1.56 2.69 2.69 0 0 1-1 2.11 6.66 6.66 0 0 1-2.38 1.28 9.33 9.33 0 0 1-2.46.45 4 4 0 0 0 .42 2.13 1.68 1.68 0 0 0 1.6.91 3.65 3.65 0 0 0 1.55-.36 4.37 4.37 0 0 0 1.38-1l.39.65a4.43 4.43 0 0 1-1.48 1.23Zm-2.4-8a4.67 4.67 0 0 0-1 1.65 7 7 0 0 0-.44 1.94 5.79 5.79 0 0 0 1.85-.39 4.25 4.25 0 0 0 1.6-1 2 2 0 0 0 .65-1.46 1.5 1.5 0 0 0-.32-1.05 1.17 1.17 0 0 0-.89-.35 1.93 1.93 0 0 0-1.45.67ZM351.91 29.91a3.08 3.08 0 0 0-1.24-.24 2.15 2.15 0 0 0-1.3.35 1.18 1.18 0 0 0-.49 1 1.54 1.54 0 0 0 .4 1.06 6.17 6.17 0 0 0 1.13 1c.42.33.76.61 1 .85a3.35 3.35 0 0 1 .67.87 2.38 2.38 0 0 1 .3 1.2 2.4 2.4 0 0 1-1 2.07 4.21 4.21 0 0 1-2.53.73 7.55 7.55 0 0 1-1.57-.17 2.73 2.73 0 0 1-1-.39l.29-1.21a3.77 3.77 0 0 0 1 .5 3.94 3.94 0 0 0 1.36.24 2.47 2.47 0 0 0 1.31-.33 1.14 1.14 0 0 0 .55-1.06 1.58 1.58 0 0 0-.43-1.09 8 8 0 0 0-1.26-1 3.53 3.53 0 0 1-1.81-2.86 2.43 2.43 0 0 1 .46-1.45 2.92 2.92 0 0 1 1.25-1 4.48 4.48 0 0 1 1.75-.34 7.2 7.2 0 0 1 1.29.12 4.56 4.56 0 0 1 .92.22l-.3 1.33a1.83 1.83 0 0 0-.75-.4ZM287 50.81h8.32l-.12 2.79h-1l-.28-1.84-4-.14-.67 5 4.07-.14-.12 1.32-4-.14-.81 5.34 4.95-.21 1-2.12 1 .19-.71 3h-9.33l.07-.68 1.32-.21 1.4-11.19-1.19-.2ZM301.65 54.52a3.52 3.52 0 0 1 2-.64 1.89 1.89 0 0 1 1.51.6 2.89 2.89 0 0 1 .53 1.94 16.85 16.85 0 0 1-.39 2.69l-.07.4-.14.84a12.68 12.68 0 0 0-.28 2.13c0 .31.07.47.23.47a1.41 1.41 0 0 0 .82-.44l.14.49a1.76 1.76 0 0 1-.37.4 3.17 3.17 0 0 1-.69.45 2 2 0 0 1-.9.2A1 1 0 0 1 303 63a14.6 14.6 0 0 1 .32-2.14l.16-.84.07-.42c.11-.64.21-1.19.28-1.66a9.18 9.18 0 0 0 .1-1.33 2 2 0 0 0-.23-1.11 1 1 0 0 0-.84-.31 2.59 2.59 0 0 0-1.57.7 6.6 6.6 0 0 0-1.48 1.67l-.86 6.33h-1.67l1.13-8.49-.86-.42.14-.66 2.14-.39.37.19-.23 2.11a6.56 6.56 0 0 1 1.68-1.71ZM313.74 66.64a4.23 4.23 0 0 1-1.77 1.2 5.86 5.86 0 0 1-2 .37 7.37 7.37 0 0 1-1.13-.09 4.89 4.89 0 0 1-.87-.22l.37-1.42a6.44 6.44 0 0 0 1 .39 4.29 4.29 0 0 0 1.22.18 2.62 2.62 0 0 0 1.66-.43 2.58 2.58 0 0 0 .71-1.62l.33-2.33a4.25 4.25 0 0 1-1.18 1 3 3 0 0 1-1.52.39 2.52 2.52 0 0 1-2.17-1 4.5 4.5 0 0 1-.72-2.68 7.33 7.33 0 0 1 .66-3 6.45 6.45 0 0 1 1.95-2.49 4.73 4.73 0 0 1 3-1 5.1 5.1 0 0 1 1 .11 5.19 5.19 0 0 1 .91.28l1.09-.39-1.58 10.63a3.73 3.73 0 0 1-.96 2.12ZM313 54.81a2.66 2.66 0 0 0-2 .85 5.43 5.43 0 0 0-1.22 2.11 7.91 7.91 0 0 0-.4 2.46 3.81 3.81 0 0 0 .42 2 1.31 1.31 0 0 0 1.17.71 2.42 2.42 0 0 0 1.37-.44 3.83 3.83 0 0 0 1-1l.93-6.28a2.13 2.13 0 0 0-1.27-.41ZM320.16 62.51a.56.56 0 0 0 .08.32.24.24 0 0 0 .2.12.8.8 0 0 0 .4-.12 4.16 4.16 0 0 0 .5-.41l.23.42a3.57 3.57 0 0 1-.78.78 2 2 0 0 1-1.24.4 1.32 1.32 0 0 1-.89-.27.92.92 0 0 1-.25-.82c0-.29.18-1.43.46-3.4.16-1.07.36-2.48.59-4.23l-1.09-.4.11-.6 2.49-.4.39.19-1.18 8.25Zm-.08-10.81a.93.93 0 0 1-.27-.68 1.25 1.25 0 0 1 .35-.89 1 1 0 0 1 .81-.37.93.93 0 0 1 .7.27.9.9 0 0 1 .27.66 1.36 1.36 0 0 1-.34.92 1.11 1.11 0 0 1-.88.37.87.87 0 0 1-.64-.28ZM328.56 54.52a3.54 3.54 0 0 1 2-.64 1.89 1.89 0 0 1 1.51.6 2.89 2.89 0 0 1 .53 1.94 16.85 16.85 0 0 1-.39 2.69l-.07.4-.14.84a12.68 12.68 0 0 0-.28 2.13c0 .31.08.47.23.47a1.41 1.41 0 0 0 .82-.44l.23.49a1.76 1.76 0 0 1-.37.4 3.17 3.17 0 0 1-.69.45 2 2 0 0 1-.9.2 1 1 0 0 1-1.16-1.05 14.6 14.6 0 0 1 .32-2.14l.16-.84.07-.42c.11-.64.21-1.19.28-1.66a9.18 9.18 0 0 0 .1-1.33 2 2 0 0 0-.23-1.11 1 1 0 0 0-.84-.31 2.59 2.59 0 0 0-1.57.7 6.6 6.6 0 0 0-1.48 1.67l-.86 6.33h-1.67l1.13-8.49-.86-.42.14-.66 2.14-.39.37.19-.23 2.11a6.56 6.56 0 0 1 1.71-1.71ZM340.41 63.44a4.26 4.26 0 0 1-2.23.6 3.35 3.35 0 0 1-1.95-.54 3 3 0 0 1-1.15-1.4 4.66 4.66 0 0 1-.37-1.87 7.38 7.38 0 0 1 .67-3.14 5.91 5.91 0 0 1 1.86-2.33 4.29 4.29 0 0 1 2.62-.88 2.62 2.62 0 0 1 1.88.6 2 2 0 0 1 .63 1.56 2.63 2.63 0 0 1-1 2.1 6.47 6.47 0 0 1-2.37 1.28 9.38 9.38 0 0 1-2.46.46A4 4 0 0 0 337 62a1.69 1.69 0 0 0 1.6.9 3.61 3.61 0 0 0 1.54-.36 4.27 4.27 0 0 0 1.39-1l.39.65a4.68 4.68 0 0 1-1.51 1.25Zm-2.4-8a4.53 4.53 0 0 0-1 1.65 6.69 6.69 0 0 0-.44 1.94 6.13 6.13 0 0 0 1.85-.39 4.25 4.25 0 0 0 1.6-1 2 2 0 0 0 .65-1.46 1.55 1.55 0 0 0-.32-1.05 1.14 1.14 0 0 0-.89-.36 2 2 0 0 0-1.46.68ZM349.39 63.44a4.26 4.26 0 0 1-2.23.6 3.35 3.35 0 0 1-2-.54 3.09 3.09 0 0 1-1.15-1.4 4.66 4.66 0 0 1-.37-1.87 7.38 7.38 0 0 1 .68-3.14 5.91 5.91 0 0 1 1.86-2.33 4.25 4.25 0 0 1 2.62-.88 2.65 2.65 0 0 1 1.88.6 2 2 0 0 1 .63 1.56 2.66 2.66 0 0 1-1 2.1 6.51 6.51 0 0 1-2.31 1.28 9.38 9.38 0 0 1-2.46.46 3.94 3.94 0 0 0 .43 2.13 1.66 1.66 0 0 0 1.59.9 3.65 3.65 0 0 0 1.55-.36 4.34 4.34 0 0 0 1.38-1l.39.65a4.68 4.68 0 0 1-1.49 1.24Zm-2.4-8a4.67 4.67 0 0 0-1 1.65 7 7 0 0 0-.44 1.94 6.07 6.07 0 0 0 1.85-.39 4.38 4.38 0 0 0 1.61-1 2 2 0 0 0 .65-1.46 1.5 1.5 0 0 0-.33-1.05 1.14 1.14 0 0 0-.89-.36 2 2 0 0 0-1.44.68ZM356.34 55.24a4.21 4.21 0 0 1 1.13-1 2.81 2.81 0 0 1 1.4-.38.93.93 0 0 1 .56.12l-.37 1.86a1.64 1.64 0 0 0-.86-.18 2.68 2.68 0 0 0-1.48.5 3.31 3.31 0 0 0-1.14 1.4l-.8 6.24h-1.69l1.11-8.45-.88-.44.12-.65 2.07-.4.35.21-.12 1.56-.08.7a3.9 3.9 0 0 1 .68-1.09ZM362.32 62.51a.56.56 0 0 0 .08.32.23.23 0 0 0 .2.12.8.8 0 0 0 .4-.12 4.16 4.16 0 0 0 .5-.41l.22.42a3.18 3.18 0 0 1-.78.78 2 2 0 0 1-1.23.4 1.3 1.3 0 0 1-.89-.27.92.92 0 0 1-.25-.82c0-.29.17-1.43.45-3.4.17-1.07.36-2.48.6-4.23l-1.09-.4.11-.6 2.49-.4.38.19-1.17 8.25Zm-.08-10.81a.93.93 0 0 1-.24-.7 1.24 1.24 0 0 1 .34-.89 1.07 1.07 0 0 1 .82-.37.94.94 0 0 1 .7.27.93.93 0 0 1 .26.66 1.35 1.35 0 0 1-.33.92 1.12 1.12 0 0 1-.88.37.86.86 0 0 1-.67-.26ZM370.36 54.52a3.55 3.55 0 0 1 2-.64 1.91 1.91 0 0 1 1.51.6 2.89 2.89 0 0 1 .52 1.94 17.7 17.7 0 0 1-.38 2.69l-.07.4-.14.84a12.68 12.68 0 0 0-.28 2.13c0 .31.07.47.22.47a1.4 1.4 0 0 0 .83-.44l.21.46a1.76 1.76 0 0 1-.37.4 3.74 3.74 0 0 1-.69.45 2.13 2.13 0 0 1-.91.2 1 1 0 0 1-1.1-1.07 14.1 14.1 0 0 1 .31-2.14l.16-.84.07-.42c.12-.64.21-1.19.28-1.66a9.27 9.27 0 0 0 .11-1.33 1.88 1.88 0 0 0-.24-1.11 1 1 0 0 0-.83-.31 2.59 2.59 0 0 0-1.57.7 6.6 6.6 0 0 0-1.48 1.67l-.86 6.33H366l1.12-8.49-.86-.42.14-.66 2.14-.39.37.19-.23 2.11a6.72 6.72 0 0 1 1.68-1.66ZM382.46 66.64a4.23 4.23 0 0 1-1.77 1.2 5.87 5.87 0 0 1-2 .37 7.34 7.34 0 0 1-1.12-.09 4.82 4.82 0 0 1-.88-.22l.37-1.42a6.58 6.58 0 0 0 1 .39 4.24 4.24 0 0 0 1.22.18 2.57 2.57 0 0 0 1.65-.43 2.53 2.53 0 0 0 .72-1.62l.33-2.33a4.25 4.25 0 0 1-1.18 1 3.07 3.07 0 0 1-1.52.39 2.52 2.52 0 0 1-2.17-1 4.5 4.5 0 0 1-.73-2.68 7.35 7.35 0 0 1 .67-3 6.27 6.27 0 0 1 1.95-2.51 4.71 4.71 0 0 1 3-1 5.1 5.1 0 0 1 1 .11 5.47 5.47 0 0 1 .91.28l1.09-.39-1.58 10.63a3.86 3.86 0 0 1-.96 2.14Zm-.7-11.83a2.62 2.62 0 0 0-2 .85 5.31 5.31 0 0 0-1.22 2.11 7.93 7.93 0 0 0-.41 2.46 3.7 3.7 0 0 0 .43 2 1.31 1.31 0 0 0 1.17.71 2.42 2.42 0 0 0 1.37-.44 3.79 3.79 0 0 0 1-1l.93-6.28a2.08 2.08 0 0 0-1.27-.41ZM295.85 80.3q1.44-3.12 1.89-4.29h3.76l-.07.75-1.56.19-.34 11.2 1.49.21-.02.64h-4.82l.07-.68 1.6-.21.4-7.76.23-3.56L297.1 80l-4.1 9.08-.94.12-1.44-9-.55-3.33-.71 3.4-1.88 7.9 1.77.21-.07.68h-4.53l.07-.68 1.46-.21L289 77l-1.62-.19.11-.75h4.07l1.35 8.56.23 1.79.77-1.76q.49-1.22 1.94-4.35ZM308 88.64a4.35 4.35 0 0 1-2.23.59 3.38 3.38 0 0 1-2-.53 3.26 3.26 0 0 1-1.15-1.4 4.87 4.87 0 0 1-.36-1.87 7.34 7.34 0 0 1 .67-3.14 6 6 0 0 1 1.91-2.29 4.32 4.32 0 0 1 2.62-.87 2.63 2.63 0 0 1 1.88.59 2.06 2.06 0 0 1 .63 1.56 2.65 2.65 0 0 1-1 2.11 6.62 6.62 0 0 1-2.37 1.28 10 10 0 0 1-2.46.46 3.89 3.89 0 0 0 .42 2.13 1.69 1.69 0 0 0 1.6.9 3.61 3.61 0 0 0 1.54-.36 4.3 4.3 0 0 0 1.39-1l.38.65a4.52 4.52 0 0 1-1.47 1.19Zm-2.41-8a4.68 4.68 0 0 0-1 1.64 7.5 7.5 0 0 0-.44 1.94 6.11 6.11 0 0 0 1.86-.38 4.61 4.61 0 0 0 1.6-1 2 2 0 0 0 .65-1.47 1.54 1.54 0 0 0-.32-1 1.15 1.15 0 0 0-.89-.36 2 2 0 0 0-1.45.64ZM318.78 87.71c0 .29.09.44.26.44a1.42 1.42 0 0 0 .81-.44l.24.44a3.31 3.31 0 0 1-.76.71 1.9 1.9 0 0 1-1.15.36c-.69 0-1-.38-1-1.13v-.38a4.57 4.57 0 0 1-1.23 1.07 3.18 3.18 0 0 1-1.65.44 2.46 2.46 0 0 1-2.14-1 4.54 4.54 0 0 1-.72-2.68 7.24 7.24 0 0 1 .67-3 6.3 6.3 0 0 1 1.89-2.48 4.67 4.67 0 0 1 3-1 4.42 4.42 0 0 1 1.31.21l.48-3.16-1.16-.3.14-.61 2.47-.32.39.23-1.83 12.4a.59.59 0 0 0-.02.2Zm-2-7.7a2.62 2.62 0 0 0-2 .85 5.14 5.14 0 0 0-1.21 2.1 8 8 0 0 0-.4 2.47 3.83 3.83 0 0 0 .42 2 1.27 1.27 0 0 0 1.16.7 2.39 2.39 0 0 0 1.4-.46 3.7 3.7 0 0 0 1-1l.95-6.19a2.2 2.2 0 0 0-1.32-.48ZM324.44 87.71a.56.56 0 0 0 .08.32.25.25 0 0 0 .21.12.79.79 0 0 0 .39-.13 3.18 3.18 0 0 0 .5-.4l.23.42a3.35 3.35 0 0 1-.78.77 2 2 0 0 1-1.24.41 1.34 1.34 0 0 1-.89-.28.92.92 0 0 1-.25-.81c0-.29.18-1.43.46-3.41.16-1.06.36-2.47.59-4.22l-1.08-.41.1-.59 2.49-.41.39.2-1.18 8.24Zm-.07-10.81a1 1 0 0 1-.28-.68 1.29 1.29 0 0 1 .35-.9 1.1 1.1 0 0 1 .81-.37.92.92 0 0 1 1 .93 1.29 1.29 0 0 1-.34.92 1.11 1.11 0 0 1-.87.38.84.84 0 0 1-.67-.28ZM332.76 80.18a2.22 2.22 0 0 0-1.53.62 4.15 4.15 0 0 0-1.06 1.74 8 8 0 0 0-.37 2.55 4.09 4.09 0 0 0 .49 2.24 1.59 1.59 0 0 0 1.42.75 2.71 2.71 0 0 0 1.29-.28 5.56 5.56 0 0 0 1.15-.81l.35.65a4.84 4.84 0 0 1-1.3 1.08 3.94 3.94 0 0 1-2 .5 2.78 2.78 0 0 1-2.31-1 4.49 4.49 0 0 1-.83-2.9 7.35 7.35 0 0 1 .6-2.87 6.1 6.1 0 0 1 1.72-2.45 4.26 4.26 0 0 1 2.77-.94 5.66 5.66 0 0 1 1.06.1 3.31 3.31 0 0 1 .92.3l-.47 1.7-.3-.1a2.88 2.88 0 0 0-1.6-.88ZM338.88 87.71a.56.56 0 0 0 .12.29.23.23 0 0 0 .2.12.82.82 0 0 0 .4-.13 3.18 3.18 0 0 0 .5-.4l.23.42a3.56 3.56 0 0 1-.78.77 2 2 0 0 1-1.24.41 1.32 1.32 0 0 1-.89-.28.9.9 0 0 1-.25-.81c0-.29.18-1.43.46-3.41.16-1.06.36-2.47.59-4.22l-1.09-.41.11-.59 2.49-.41.39.2-1.18 8.24Zm-.08-10.81a1 1 0 0 1-.27-.68 1.29 1.29 0 0 1 .35-.9 1.07 1.07 0 0 1 .81-.37.92.92 0 0 1 1 .93 1.34 1.34 0 0 1-.34.92 1.11 1.11 0 0 1-.88.38.87.87 0 0 1-.67-.28ZM347.19 79.72a3.54 3.54 0 0 1 2-.64 1.89 1.89 0 0 1 1.51.59 2.93 2.93 0 0 1 .53 2 16.77 16.77 0 0 1-.39 2.68l-.07.41-.14.84a12.6 12.6 0 0 0-.28 2.12c0 .32.08.48.23.48a1.38 1.38 0 0 0 .82-.44l.21.45a1.91 1.91 0 0 1-.36.41 3.11 3.11 0 0 1-.7.44 1.93 1.93 0 0 1-.9.21 1 1 0 0 1-1.11-1.07 14.24 14.24 0 0 1 .32-2.14l.16-.85.07-.42c.11-.63.21-1.18.28-1.66a9 9 0 0 0 .1-1.32 1.87 1.87 0 0 0-.23-1.11 1 1 0 0 0-.84-.31 2.66 2.66 0 0 0-1.57.69 6.48 6.48 0 0 0-1.48 1.68l-.89 6.24h-1.66l1.12-8.49-.86-.42.14-.67 2.14-.38.37.19-.23 2.1a6.52 6.52 0 0 1 1.71-1.61ZM359 88.64a4.35 4.35 0 0 1-2.23.59 3.34 3.34 0 0 1-1.95-.53 3.19 3.19 0 0 1-1.15-1.4 4.69 4.69 0 0 1-.37-1.87 7.34 7.34 0 0 1 .67-3.14 6 6 0 0 1 1.9-2.29 4.35 4.35 0 0 1 2.63-.87 2.61 2.61 0 0 1 1.87.59 2 2 0 0 1 .64 1.56 2.68 2.68 0 0 1-1 2.11 6.75 6.75 0 0 1-2.38 1.28 9.81 9.81 0 0 1-2.46.46 4.08 4.08 0 0 0 .42 2.13 1.69 1.69 0 0 0 1.6.9 3.65 3.65 0 0 0 1.55-.36 4.37 4.37 0 0 0 1.38-1l.39.65a4.57 4.57 0 0 1-1.51 1.19Zm-2.4-8a4.54 4.54 0 0 0-1 1.64 6.76 6.76 0 0 0-.44 1.94 6 6 0 0 0 1.85-.38 4.52 4.52 0 0 0 1.6-1 2 2 0 0 0 .65-1.47 1.49 1.49 0 0 0-.32-1 1.14 1.14 0 0 0-.89-.36 2 2 0 0 0-1.41.64Z" class="cls-2" transform="translate(-24.97 -24.05)"/> </svg> </a> </div> <div class="global-nav__controls"><button class="controls__menu"> Close <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class=""><path fill-rule="evenodd" d="M20.728 8l1.818 1.818-5.455 5.455 5.455 5.455-1.818 1.818-5.455-5.455-5.455 5.455L8 20.728l5.455-5.455L8 9.818 9.818 8l5.455 5.455z"></path></svg> </button> </div></div> <div class="mega-menu__content"><div> <button class="accordion">About Us</button> <div class="panel"><ul><li><a href="https://www.nationalacademies.org/about"> About Us </a></li><li><a href="https://www.nationalacademies.org/about/organization"> Our Program Divisions </a></li><li><a href="https://www.nationalacademies.org/about/the-national-academies"> Our Three Academies </a></li><li><a href="https://www.nationalacademies.org/about/leadership"> Leadership </a></li><li><a href="https://www.nationalacademies.org/newsroom"> Newsroom </a></li><li><a href="https://www.nationalacademies.org/ocga"> Government Affairs </a></li><li><a href="https://www.nationalacademies.org/giving"> Giving </a></li><li><a href="https://www.nationalacademies.org/about/institutional-policies-and-procedures/statement-on-diversity-and-inclusion"> Statement on Diversity and Inclusion </a></li></ul> </div> <button class="no-accordion"><a href="https://www.nationalacademies.org/events">Events</a></button> <button class="accordion">Our Work</button> <div class="panel"><ul><li><a href="https://www.nationalacademies.org/our-work"> Our Work </a></li><li><a href="https://www.nationalacademies.org/about/our-study-process"> Our Study Process </a></li><li><a href="https://www.nationalacademies.org/about/institutional-policies-and-procedures/conflict-of-interest-policies-and-procedures"> Conflict of Interest Policies and Procedures </a></li><li><a href="https://www.nationalacademies.org/about/institutional-policies-and-procedures/project-comments-and-information"> Project Comments and Information </a></li></ul> </div> <button class="accordion">Publications</button> <div class="panel"> <ul><li><a href="https://nap.nationalacademies.org/" target="_self"> Read Our Expert Reports and Published Proceedings </a></li><li><a href="https://www.pnas.org/" target="_self"> Explore PNAS, the Flagship Scientific Journal of NAS </a></li><li><a href="http://pubsindex.trb.org" target="_self"> Access Transportation Research Board Publications </a></li></ul> </div> <button class="accordion">Topics</button> <div class="panel"> <ul><li><a href="https://www.nationalacademies.org/topics/covid-19-resources"> Coronavirus Disease 2019 (COVID-19) </a></li><li><a href="https://www.nationalacademies.org/topics/resources-on-diversity-equity-and-inclusion"> Diversity, Equity, and Inclusion </a></li><li><a href="https://www.nationalacademies.org/topics/climate"> Climate </a></li><li><a href="https://www.nationalacademies.org/topics/economic-recovery"> Economic Recovery </a></li></ul> </div> <button class="no-accordion"><a href="https://www.nationalacademies.org/engagement">Engagement</a></button> <button class="accordion">Opportunities</button> <div class="panel"> <ul><li><a href="https://www.nationalacademies.org/careers"> Careers </a></li><li><a href="https://www.nationalacademies.org/fellowships-and-grants"> Fellowships and Grants </a></li><li><a href="https://www.nationalacademies.org/about/volunteers"> Volunteers </a></li><li><a href="https://www.nationalacademies.org/about/sponsors"> Sponsors </a></li><li><a href="https://www.nationalacademies.org/about/members"> Members </a></li></ul> </div> </div></div> </div> </div>  </div> <div class="container flex justify-between"> <div class="global-nav__logo" > <a class="navbar-brand js-scroll-trigger" aria-label="Logo of The National Academies" href="https://www.nationalacademies.org/home"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 315.11 58.33"> <defs><style>.cls-2{fill:#211747;}</style></defs><g id="Layer_2" data-name="Layer 2"><g id="Layer_1-2" data-name="Layer 1"><polygon class="cls-2" points="3.73 7.55 20.84 25.49 20.84 1.5 17.81 1.5 17.81 18.08 0.7 0.14 0.7 24.06 3.73 24.06 3.73 7.55"/><polygon class="cls-2" points="28.49 24.06 31.84 24.06 38.98 7.25 45.92 23.87 45.99 24.06 49.34 24.06 39.05 0 28.49 24.06"/><polygon class="cls-2" points="153.23 24.06 156.58 24.06 163.72 7.25 170.66 23.87 170.73 24.06 174.08 24.06 163.79 0 153.23 24.06"/><polygon class="cls-2" points="59.72 24.06 62.76 24.06 62.76 4.41 69.52 4.41 69.52 1.5 52.96 1.5 52.96 4.41 59.72 4.41 59.72 24.06"/><rect class="cls-2" x="78.85" y="1.5" width="3.03" height="22.55"/><path class="cls-2" d="M115.69,12.8a11.72,11.72,0,0,0-23.44,0,11.72,11.72,0,0,0,23.44,0m-3.09,0A8.63,8.63,0,1,1,104,4a8.7,8.7,0,0,1,8.63,8.76"/><polygon class="cls-2" points="128.29 7.55 145.4 25.49 145.4 1.5 142.37 1.5 142.37 18.08 125.25 0.14 125.25 24.06 128.29 24.06 128.29 7.55"/><polygon class="cls-2" points="184.65 1.5 181.62 1.5 181.62 24.06 193.7 24.06 193.7 21.16 184.65 21.16 184.65 1.5"/><path class="cls-2" d="M37.15,34.08A11.48,11.48,0,0,0,25.37,45.8,11.36,11.36,0,0,0,37,57.38a11.77,11.77,0,0,0,6.79-2.19l.13-.09V51.2l-.51.51A9.77,9.77,0,0,1,41,53.5a8.9,8.9,0,0,1-3.95,1A8.75,8.75,0,0,1,37,37a9.09,9.09,0,0,1,3.66.82,10.71,10.71,0,0,1,2.78,2l.51.5V36.4l-.12-.09a10.62,10.62,0,0,0-6.67-2.23"/><path class="cls-2" d="M91.91,37.08a12.19,12.19,0,0,0-8.29-2.64H78.85V57h4.74c3.72,0,6-.73,8.22-2.61a10.75,10.75,0,0,0,4-8.65,11,11,0,0,0-3.86-8.65m-2.09,15.1a9.11,9.11,0,0,1-6.1,1.91H81.88V37.34h1.84c5.44,0,9,3.29,9,8.39a8.09,8.09,0,0,1-2.85,6.45"/><polygon class="cls-2" points="104.99 56.99 118.4 56.99 118.4 54.09 108.02 54.09 108.02 46.16 117.11 46.16 117.11 43.26 108.02 43.26 108.02 37.34 118.4 37.34 118.4 34.44 104.99 34.44 104.99 56.99"/><polygon class="cls-2" points="176.17 56.99 189.58 56.99 189.58 54.09 179.2 54.09 179.2 46.16 188.28 46.16 188.28 43.26 179.2 43.26 179.2 37.34 189.58 37.34 189.58 34.44 176.17 34.44 176.17 56.99"/><polygon class="cls-2" points="138.88 51.34 130.31 32.49 126.44 56.99 129.55 56.99 131.62 42.47 138.84 58.33 146.15 42.47 148.13 56.99 151.23 56.99 147.61 32.45 138.88 51.34"/><rect class="cls-2" x="161.31" y="34.44" width="3.03" height="22.55"/><path class="cls-2" d="M209,46.15A10.78,10.78,0,0,0,205.49,44l-2.12-.92a6.8,6.8,0,0,1-2.21-1.33,2,2,0,0,1-.73-1.69A3.07,3.07,0,0,1,203.82,37a3.62,3.62,0,0,1,2.28.69,4.87,4.87,0,0,1,1.2,1.55l.15.3,2.45-1.62-.12-.24a7,7,0,0,0-2.24-2.55,6.34,6.34,0,0,0-3.69-1c-3.8,0-6.45,2.45-6.45,6a4.86,4.86,0,0,0,1.6,3.8,9.51,9.51,0,0,0,2.84,1.78l2.15,1a9.5,9.5,0,0,1,2.56,1.46,3,3,0,0,1,1,2.35,4.2,4.2,0,0,1-7.06,2.92,4.93,4.93,0,0,1-1.24-2.64l-.05-.33-3,.82.06.28a8.32,8.32,0,0,0,2.13,4,6.74,6.74,0,0,0,5,1.87,6.91,6.91,0,0,0,7.24-7A5.58,5.58,0,0,0,209,46.15"/><polygon class="cls-2" points="0 56.99 3.35 56.99 10.49 40.18 17.43 56.81 17.5 56.99 20.86 56.99 10.56 32.93 0 56.99"/><polygon class="cls-2" points="50.21 56.99 53.57 56.99 60.71 40.18 67.64 56.81 67.72 56.99 71.07 56.99 60.78 32.93 50.21 56.99"/><path class="cls-2" d="M233.74,2.1a3.34,3.34,0,0,0-.93-.11,2.53,2.53,0,0,0-1.52.45,1.48,1.48,0,0,0-.63,1.28,2,2,0,0,0,.54,1.44,7.94,7.94,0,0,0,1.64,1.26,13.5,13.5,0,0,1,1.26.89,3.76,3.76,0,0,1,.83,1,2.62,2.62,0,0,1,.33,1.33,3.06,3.06,0,0,1-.5,1.74,3.26,3.26,0,0,1-1.4,1.18,5.06,5.06,0,0,1-2.09.41,8.3,8.3,0,0,1-1.94-.22,3.51,3.51,0,0,1-1.24-.46l.34-2.18h.92l.09,1.62a2.53,2.53,0,0,0,.81.33,3.86,3.86,0,0,0,1,.13,2.93,2.93,0,0,0,1.77-.53,1.68,1.68,0,0,0,.73-1.47,1.91,1.91,0,0,0-.49-1.34,6.42,6.42,0,0,0-1.49-1.16c-.52-.34-1-.65-1.32-.94a3.76,3.76,0,0,1-.9-1,2.64,2.64,0,0,1-.37-1.4,2.64,2.64,0,0,1,.5-1.62,3.23,3.23,0,0,1,1.35-1.08,4.58,4.58,0,0,1,1.86-.37,7,7,0,0,1,1.72.18,3.31,3.31,0,0,1,1.09.45l-.35,2h-.83l-.12-1.47a2.39,2.39,0,0,0-.68-.3"/><path class="cls-2" d="M241,5a2,2,0,0,0-1.35.54,3.66,3.66,0,0,0-.92,1.52,7,7,0,0,0-.33,2.24,3.52,3.52,0,0,0,.43,1.95,1.39,1.39,0,0,0,1.24.66,2.38,2.38,0,0,0,1.1-.24,5.05,5.05,0,0,0,1-.72l.3.57a3.84,3.84,0,0,1-1.14.95,3.43,3.43,0,0,1-1.76.43,2.44,2.44,0,0,1-2-.91,4,4,0,0,1-.73-2.54A6.43,6.43,0,0,1,237.34,7a5.3,5.3,0,0,1,1.55-2.08,3.74,3.74,0,0,1,2.42-.83,5,5,0,0,1,.93.09,3.09,3.09,0,0,1,.81.26l-.42,1.49-.26-.09A2.53,2.53,0,0,0,241,5"/><path class="cls-2" d="M246.1,11.61a.56.56,0,0,0,.07.29.21.21,0,0,0,.18.1.65.65,0,0,0,.34-.11,2.64,2.64,0,0,0,.44-.35l.2.37a2.88,2.88,0,0,1-.68.67,1.71,1.71,0,0,1-1.08.35,1.14,1.14,0,0,1-.78-.23.8.8,0,0,1-.22-.72c0-.25.15-1.25.4-3,.14-.93.31-2.16.52-3.7l-1-.35.09-.52,2.18-.36.34.17-1,7.22ZM246,2.15a.84.84,0,0,1-.23-.59,1.13,1.13,0,0,1,.3-.79.94.94,0,0,1,.71-.32.79.79,0,0,1,.61.24.77.77,0,0,1,.23.57,1.15,1.15,0,0,1-.29.81,1,1,0,0,1-.77.33.75.75,0,0,1-.56-.25"/><path class="cls-2" d="M254,12.43a3.75,3.75,0,0,1-1.95.52,3,3,0,0,1-1.72-.47,2.74,2.74,0,0,1-1-1.23A4,4,0,0,1,249,9.62a6.35,6.35,0,0,1,.59-2.75,5.08,5.08,0,0,1,1.63-2,3.7,3.7,0,0,1,2.29-.77,2.27,2.27,0,0,1,1.64.52A1.79,1.79,0,0,1,255.72,6a2.34,2.34,0,0,1-.89,1.84,5.79,5.79,0,0,1-2.08,1.12,8.1,8.1,0,0,1-2.15.4,3.42,3.42,0,0,0,.37,1.87,1.48,1.48,0,0,0,1.4.79,3.18,3.18,0,0,0,1.35-.32,3.75,3.75,0,0,0,1.21-.9l.34.57A4,4,0,0,1,254,12.43m-2.11-7A4.1,4.1,0,0,0,251,6.88a5.9,5.9,0,0,0-.39,1.69,5.31,5.31,0,0,0,1.62-.33,4,4,0,0,0,1.41-.87,1.76,1.76,0,0,0,.57-1.28,1.33,1.33,0,0,0-.29-.92,1,1,0,0,0-.77-.31,1.74,1.74,0,0,0-1.28.57"/><path class="cls-2" d="M261.24,4.62A3.14,3.14,0,0,1,263,4.06a1.67,1.67,0,0,1,1.32.52,2.61,2.61,0,0,1,.46,1.71,15.44,15.44,0,0,1-.34,2.34l-.06.36-.13.74a11.51,11.51,0,0,0-.24,1.85c0,.28.06.42.2.42a1.22,1.22,0,0,0,.72-.39l.18.4a1.54,1.54,0,0,1-.32.36,2.92,2.92,0,0,1-.61.39,1.73,1.73,0,0,1-.79.17.84.84,0,0,1-1-.93,12.88,12.88,0,0,1,.27-1.88l.14-.73.06-.37c.1-.55.19-1,.25-1.45a8.17,8.17,0,0,0,.09-1.16,1.67,1.67,0,0,0-.21-1,.87.87,0,0,0-.73-.27,2.33,2.33,0,0,0-1.37.61,5.75,5.75,0,0,0-1.3,1.47l-.75,5.54h-1.46l1-7.43L257.62,5l.12-.58,1.88-.34.32.17-.2,1.84a5.72,5.72,0,0,1,1.5-1.45"/><path class="cls-2" d="M270.77,5a2,2,0,0,0-1.35.54,3.66,3.66,0,0,0-.92,1.52,7,7,0,0,0-.33,2.24,3.52,3.52,0,0,0,.43,1.95,1.39,1.39,0,0,0,1.24.66,2.38,2.38,0,0,0,1.1-.24,5.05,5.05,0,0,0,1-.72l.3.57a3.84,3.84,0,0,1-1.14.95,3.43,3.43,0,0,1-1.76.43,2.44,2.44,0,0,1-2-.91,4,4,0,0,1-.73-2.54A6.43,6.43,0,0,1,267.13,7a5.3,5.3,0,0,1,1.55-2.08,3.76,3.76,0,0,1,2.42-.83,5,5,0,0,1,.93.09,3,3,0,0,1,.81.26l-.42,1.49-.26-.09A2.53,2.53,0,0,0,270.77,5"/><path class="cls-2" d="M278.66,12.43a3.75,3.75,0,0,1-2,.52,3,3,0,0,1-1.71-.47,2.7,2.7,0,0,1-1-1.23,4.19,4.19,0,0,1-.32-1.63,6.35,6.35,0,0,1,.59-2.75,5.17,5.17,0,0,1,1.63-2,3.7,3.7,0,0,1,2.29-.77,2.32,2.32,0,0,1,1.65.52A1.82,1.82,0,0,1,280.38,6a2.34,2.34,0,0,1-.89,1.84,5.79,5.79,0,0,1-2.08,1.12,8,8,0,0,1-2.15.4,3.51,3.51,0,0,0,.37,1.87A1.48,1.48,0,0,0,277,12a3.18,3.18,0,0,0,1.35-.32,3.75,3.75,0,0,0,1.21-.9l.34.57a4,4,0,0,1-1.27,1.11m-2.11-7a4.25,4.25,0,0,0-.87,1.45,6.25,6.25,0,0,0-.39,1.69,5.44,5.44,0,0,0,1.63-.33,4.05,4.05,0,0,0,1.4-.87,1.76,1.76,0,0,0,.57-1.28,1.33,1.33,0,0,0-.29-.92,1,1,0,0,0-.77-.31,1.74,1.74,0,0,0-1.28.57"/><path class="cls-2" d="M286.18,5.13a2.75,2.75,0,0,0-1.09-.21,1.85,1.85,0,0,0-1.13.31,1,1,0,0,0-.43.89,1.43,1.43,0,0,0,.34.93,6.08,6.08,0,0,0,1,.88,10.43,10.43,0,0,1,.88.74,3.1,3.1,0,0,1,.6.76,2.15,2.15,0,0,1,.26,1.05,2.09,2.09,0,0,1-.9,1.81,3.71,3.71,0,0,1-2.22.64,6.32,6.32,0,0,1-1.37-.15,2.1,2.1,0,0,1-.9-.34l.24-1.06a3.41,3.41,0,0,0,.88.44,3.37,3.37,0,0,0,1.18.21,2.21,2.21,0,0,0,1.15-.29,1,1,0,0,0,.48-.92,1.37,1.37,0,0,0-.38-1,6.83,6.83,0,0,0-1.1-.89,3.07,3.07,0,0,1-1.58-2.5,2.16,2.16,0,0,1,.4-1.27,2.64,2.64,0,0,1,1.09-.84,3.81,3.81,0,0,1,1.54-.3,6.32,6.32,0,0,1,1.13.1,4.07,4.07,0,0,1,.8.19l-.26,1.17a1.55,1.55,0,0,0-.6-.39"/><polygon class="cls-2" points="229.34 23.43 236.61 23.43 236.51 25.87 235.6 25.87 235.35 24.25 231.87 24.13 231.29 28.48 234.85 28.36 234.74 29.51 231.21 29.38 230.58 34.05 234.91 33.87 235.77 32.01 236.63 32.18 236.01 34.84 227.85 34.84 227.91 34.24 229.06 34.05 230.29 24.25 229.24 24.09 229.34 23.43"/><path class="cls-2" d="M242.18,26.67a3.16,3.16,0,0,1,1.73-.56,1.67,1.67,0,0,1,1.32.53,2.51,2.51,0,0,1,.46,1.7,14.42,14.42,0,0,1-.34,2.35l-.06.35-.12.74a10.81,10.81,0,0,0-.25,1.86c0,.27.07.41.2.41a1.15,1.15,0,0,0,.72-.38l.19.4a1.54,1.54,0,0,1-.32.35,2.46,2.46,0,0,1-.61.39,1.76,1.76,0,0,1-.79.18c-.65,0-1-.31-1-.94a11.94,11.94,0,0,1,.28-1.87l.14-.74.06-.37c.1-.55.18-1,.24-1.45a8.14,8.14,0,0,0,.1-1.16,1.64,1.64,0,0,0-.21-1,.87.87,0,0,0-.73-.27,2.3,2.3,0,0,0-1.38.61,5.67,5.67,0,0,0-1.29,1.46l-.76,5.55h-1.45l1-7.44-.76-.36.13-.59,1.87-.34.32.17-.2,1.85a5.77,5.77,0,0,1,1.5-1.46"/><path class="cls-2" d="M252.77,37.29a4,4,0,0,1-1.55,1.05,5.36,5.36,0,0,1-1.78.32,5.69,5.69,0,0,1-1-.09,3.45,3.45,0,0,1-.76-.19l.32-1.24a5,5,0,0,0,.9.34,3.56,3.56,0,0,0,1.06.17,2.22,2.22,0,0,0,1.45-.39,2.12,2.12,0,0,0,.63-1.41l.29-2a3.73,3.73,0,0,1-1,.84A2.61,2.61,0,0,1,250,35a2.16,2.16,0,0,1-1.89-.88,3.9,3.9,0,0,1-.64-2.35,6.52,6.52,0,0,1,.58-2.6A5.62,5.62,0,0,1,249.73,27a4.15,4.15,0,0,1,2.61-.87,4.47,4.47,0,0,1,.87.1,5.15,5.15,0,0,1,.8.24l1-.34-1.38,9.31a3.37,3.37,0,0,1-.81,1.87m-.61-10.36a2.36,2.36,0,0,0-1.75.74,4.82,4.82,0,0,0-1.07,1.85,7.16,7.16,0,0,0-.35,2.15,3.3,3.3,0,0,0,.37,1.72,1.16,1.16,0,0,0,1,.62,2.09,2.09,0,0,0,1.2-.39,3.12,3.12,0,0,0,.9-.87l.82-5.5a1.85,1.85,0,0,0-1.15-.32"/><path class="cls-2" d="M258.39,33.67a.45.45,0,0,0,.07.28.19.19,0,0,0,.17.1.6.6,0,0,0,.35-.11,3.13,3.13,0,0,0,.44-.35l.2.37a3.17,3.17,0,0,1-.69.68,1.77,1.77,0,0,1-1.08.35,1.14,1.14,0,0,1-.78-.24.82.82,0,0,1-.22-.71c0-.26.16-1.25.4-3,.15-.93.32-2.17.52-3.7l-.95-.36.09-.52,2.19-.35.33.17-1,7.21Zm-.07-9.46a.81.81,0,0,1-.24-.6,1.09,1.09,0,0,1,.3-.78.94.94,0,0,1,.72-.33.81.81,0,0,1,.61.24.82.82,0,0,1,.23.58,1.17,1.17,0,0,1-.29.8,1,1,0,0,1-.77.33.76.76,0,0,1-.56-.24"/><path class="cls-2" d="M265.74,26.67a3.11,3.11,0,0,1,1.72-.56,1.65,1.65,0,0,1,1.32.53,2.5,2.5,0,0,1,.47,1.7,15.68,15.68,0,0,1-.34,2.35l-.06.35-.13.74a11.6,11.6,0,0,0-.24,1.86c0,.27.06.41.2.41a1.2,1.2,0,0,0,.72-.38l.18.4a1.54,1.54,0,0,1-.32.35,2.28,2.28,0,0,1-.61.39,1.73,1.73,0,0,1-.79.18.84.84,0,0,1-1-.94,12.8,12.8,0,0,1,.27-1.87l.14-.74.06-.37c.1-.55.19-1,.25-1.45a8.07,8.07,0,0,0,.09-1.16,1.64,1.64,0,0,0-.21-1,.87.87,0,0,0-.73-.27,2.27,2.27,0,0,0-1.37.61,5.7,5.7,0,0,0-1.3,1.46l-.75,5.55h-1.46l1-7.44-.75-.36.12-.59,1.88-.34.32.17-.2,1.85a5.77,5.77,0,0,1,1.5-1.46"/><path class="cls-2" d="M276.11,34.48a3.7,3.7,0,0,1-1.95.52,3,3,0,0,1-1.71-.46,2.87,2.87,0,0,1-1-1.23,4.24,4.24,0,0,1-.32-1.64,6.53,6.53,0,0,1,.59-2.75,5.17,5.17,0,0,1,1.63-2,3.76,3.76,0,0,1,2.29-.77,2.32,2.32,0,0,1,1.65.53,1.76,1.76,0,0,1,.55,1.36,2.31,2.31,0,0,1-.88,1.84A5.83,5.83,0,0,1,274.87,31a9.08,9.08,0,0,1-2.15.4,3.49,3.49,0,0,0,.36,1.86,1.48,1.48,0,0,0,1.4.79,3.16,3.16,0,0,0,1.35-.31,3.9,3.9,0,0,0,1.22-.9l.33.57a3.93,3.93,0,0,1-1.27,1.1m-2.1-7a4.12,4.12,0,0,0-.88,1.44,6.37,6.37,0,0,0-.38,1.7,5.17,5.17,0,0,0,1.62-.34,3.78,3.78,0,0,0,1.4-.87,1.74,1.74,0,0,0,.57-1.28,1.31,1.31,0,0,0-.28-.91,1,1,0,0,0-.78-.32,1.68,1.68,0,0,0-1.27.58"/><path class="cls-2" d="M284,34.48a3.7,3.7,0,0,1-2,.52,3,3,0,0,1-1.71-.46,2.87,2.87,0,0,1-1-1.23,4.24,4.24,0,0,1-.32-1.64,6.53,6.53,0,0,1,.59-2.75,5.26,5.26,0,0,1,1.63-2,3.79,3.79,0,0,1,2.3-.77,2.31,2.31,0,0,1,1.64.53,1.76,1.76,0,0,1,.55,1.36,2.31,2.31,0,0,1-.88,1.84A5.74,5.74,0,0,1,282.73,31a9.08,9.08,0,0,1-2.15.4,3.4,3.4,0,0,0,.37,1.86,1.45,1.45,0,0,0,1.39.79,3.2,3.2,0,0,0,1.36-.31,3.86,3.86,0,0,0,1.21-.9l.34.57a4,4,0,0,1-1.28,1.1m-2.1-7a4.12,4.12,0,0,0-.88,1.44,6.37,6.37,0,0,0-.38,1.7,5.17,5.17,0,0,0,1.62-.34,3.7,3.7,0,0,0,1.4-.87,1.74,1.74,0,0,0,.57-1.28,1.31,1.31,0,0,0-.28-.91,1,1,0,0,0-.78-.32,1.7,1.7,0,0,0-1.27.58"/><path class="cls-2" d="M290.05,27.3a3.77,3.77,0,0,1,1-.83,2.34,2.34,0,0,1,1.22-.34.83.83,0,0,1,.5.11l-.33,1.62a1.45,1.45,0,0,0-.75-.15,2.3,2.3,0,0,0-1.29.44,2.89,2.89,0,0,0-1,1.22l-.7,5.47h-1.48l1-7.41-.77-.38.11-.57,1.81-.35.31.18-.11,1.37-.08.61a4.09,4.09,0,0,1,.6-1"/><path class="cls-2" d="M295.29,33.67a.45.45,0,0,0,.07.28.19.19,0,0,0,.17.1.6.6,0,0,0,.35-.11,3.13,3.13,0,0,0,.44-.35l.2.37a3.17,3.17,0,0,1-.69.68,1.77,1.77,0,0,1-1.08.35,1.14,1.14,0,0,1-.78-.24.82.82,0,0,1-.22-.71c0-.26.16-1.25.4-3,.15-.93.32-2.17.52-3.7l-.95-.36.09-.52,2.19-.35.33.17-1,7.21Zm-.07-9.46a.81.81,0,0,1-.24-.6,1.09,1.09,0,0,1,.3-.78.94.94,0,0,1,.72-.33.81.81,0,0,1,.61.24.82.82,0,0,1,.23.58,1.17,1.17,0,0,1-.29.8,1,1,0,0,1-.77.33.76.76,0,0,1-.56-.24"/><path class="cls-2" d="M302.33,26.67a3.14,3.14,0,0,1,1.73-.56,1.67,1.67,0,0,1,1.32.53,2.56,2.56,0,0,1,.46,1.7,15.68,15.68,0,0,1-.34,2.35l-.06.35-.12.74a10.81,10.81,0,0,0-.25,1.86c0,.27.07.41.2.41a1.2,1.2,0,0,0,.72-.38l.19.4a1.64,1.64,0,0,1-.33.35,2.22,2.22,0,0,1-.6.39,1.76,1.76,0,0,1-.79.18c-.65,0-1-.31-1-.94a12.8,12.8,0,0,1,.27-1.87l.14-.74.06-.37c.11-.55.19-1,.25-1.45a8.07,8.07,0,0,0,.09-1.16,1.73,1.73,0,0,0-.2-1,.88.88,0,0,0-.73-.27,2.3,2.3,0,0,0-1.38.61,5.7,5.7,0,0,0-1.3,1.46l-.75,5.55h-1.46l1-7.44-.75-.36.13-.59,1.87-.34.32.17-.2,1.85a5.77,5.77,0,0,1,1.5-1.46"/><path class="cls-2" d="M312.92,37.29a4,4,0,0,1-1.55,1.05,5.36,5.36,0,0,1-1.78.32,5.69,5.69,0,0,1-1-.09,3.57,3.57,0,0,1-.77-.19l.33-1.24a5,5,0,0,0,.9.34,3.51,3.51,0,0,0,1.06.17,2.22,2.22,0,0,0,1.45-.39,2.11,2.11,0,0,0,.62-1.41l.3-2a3.73,3.73,0,0,1-1,.84,2.63,2.63,0,0,1-1.33.34,2.16,2.16,0,0,1-1.89-.88,3.9,3.9,0,0,1-.64-2.35,6.35,6.35,0,0,1,.58-2.6A5.62,5.62,0,0,1,309.88,27a4.11,4.11,0,0,1,2.61-.87,4.56,4.56,0,0,1,.87.1,5.15,5.15,0,0,1,.8.24l.95-.34-1.38,9.31a3.37,3.37,0,0,1-.81,1.87m-.62-10.36a2.35,2.35,0,0,0-1.74.74,4.7,4.7,0,0,0-1.07,1.85,7.16,7.16,0,0,0-.35,2.15,3.3,3.3,0,0,0,.37,1.72,1.14,1.14,0,0,0,1,.62,2,2,0,0,0,1.19-.39,3.3,3.3,0,0,0,.91-.87l.82-5.5a1.88,1.88,0,0,0-1.16-.32"/><path class="cls-2" d="M237.11,49.24c.83-1.82,1.39-3.07,1.65-3.76h3.29l-.06.66-1.37.17-.29,9.8,1.31.18-.07.6h-4.22l.06-.6,1.4-.18.35-6.79.2-3.12L238.2,49l-3.57,8-.83.11-1.26-7.89-.47-2.92-.63,3-1.64,6.91,1.55.18-.06.6h-4l.06-.6,1.28-.18,2.47-9.8-1.41-.17.09-.66h3.56L234.56,53l.2,1.57.67-1.53c.28-.69.84-1.95,1.68-3.77"/><path class="cls-2" d="M247.75,56.54a3.75,3.75,0,0,1-1.95.52,3,3,0,0,1-1.71-.47,2.7,2.7,0,0,1-1-1.23,4.19,4.19,0,0,1-.32-1.63,6.35,6.35,0,0,1,.59-2.75,5.17,5.17,0,0,1,1.63-2,3.7,3.7,0,0,1,2.29-.77,2.32,2.32,0,0,1,1.65.52,1.82,1.82,0,0,1,.55,1.37,2.34,2.34,0,0,1-.89,1.84A5.79,5.79,0,0,1,246.5,53a8,8,0,0,1-2.15.4,3.51,3.51,0,0,0,.37,1.87,1.48,1.48,0,0,0,1.4.79,3.18,3.18,0,0,0,1.35-.32,3.75,3.75,0,0,0,1.21-.9l.34.57a4,4,0,0,1-1.27,1.11m-2.11-7a4.25,4.25,0,0,0-.87,1.45,6.25,6.25,0,0,0-.39,1.69,5.44,5.44,0,0,0,1.63-.33,4.05,4.05,0,0,0,1.4-.87A1.76,1.76,0,0,0,248,50.2a1.33,1.33,0,0,0-.29-.92,1,1,0,0,0-.77-.31,1.74,1.74,0,0,0-1.28.57"/><path class="cls-2" d="M257.17,55.72q0,.39.24.39a1.19,1.19,0,0,0,.7-.39l.22.39a3.42,3.42,0,0,1-.67.62,1.68,1.68,0,0,1-1,.31c-.6,0-.9-.32-.9-1v-.34a3.94,3.94,0,0,1-1.08.94,2.72,2.72,0,0,1-1.44.38,2.13,2.13,0,0,1-1.87-.88,4,4,0,0,1-.63-2.34,6.41,6.41,0,0,1,.58-2.62A5.56,5.56,0,0,1,253,49a4.1,4.1,0,0,1,2.61-.86,4,4,0,0,1,1.15.18l.41-2.76-1-.26.13-.54,2.16-.28.34.2-1.6,10.84a.79.79,0,0,0,0,.17M255.42,49a2.32,2.32,0,0,0-1.74.75,4.64,4.64,0,0,0-1.06,1.84,7.15,7.15,0,0,0-.34,2.16,3.44,3.44,0,0,0,.36,1.72,1.12,1.12,0,0,0,1,.61,2.06,2.06,0,0,0,1.23-.41,3.11,3.11,0,0,0,.9-.91l.83-5.42a1.94,1.94,0,0,0-1.2-.34"/><path class="cls-2" d="M262.14,55.72a.57.57,0,0,0,.06.29.24.24,0,0,0,.18.1.71.71,0,0,0,.35-.11,3.84,3.84,0,0,0,.44-.35l.19.37a2.88,2.88,0,0,1-.68.67,1.71,1.71,0,0,1-1.08.35,1.19,1.19,0,0,1-.78-.23.8.8,0,0,1-.22-.72c0-.25.15-1.25.4-3,.14-.93.32-2.16.52-3.7l-.95-.35.09-.52,2.18-.36.34.17-1,7.22Zm-.07-9.46a.81.81,0,0,1-.24-.6,1.12,1.12,0,0,1,.3-.78,1,1,0,0,1,.71-.32.83.83,0,0,1,.62.24.81.81,0,0,1,.23.57,1.2,1.2,0,0,1-.29.81,1,1,0,0,1-.77.33.73.73,0,0,1-.56-.25"/><path class="cls-2" d="M269.42,49.14a2,2,0,0,0-1.35.54,3.6,3.6,0,0,0-.92,1.52,7,7,0,0,0-.33,2.24,3.52,3.52,0,0,0,.43,2,1.39,1.39,0,0,0,1.24.66,2.38,2.38,0,0,0,1.1-.24,5.05,5.05,0,0,0,1-.72l.3.57a4,4,0,0,1-1.14,1A3.43,3.43,0,0,1,268,57a2.44,2.44,0,0,1-2-.91,4,4,0,0,1-.73-2.54,6.43,6.43,0,0,1,.53-2.51A5.3,5.3,0,0,1,267.33,49a3.69,3.69,0,0,1,2.42-.83,5,5,0,0,1,.93.09,3.09,3.09,0,0,1,.81.26L271.07,50l-.26-.09a2.53,2.53,0,0,0-1.39-.78"/><path class="cls-2" d="M274.77,55.72a.56.56,0,0,0,.07.29.24.24,0,0,0,.18.1.71.71,0,0,0,.35-.11,3.15,3.15,0,0,0,.43-.35l.2.37a2.88,2.88,0,0,1-.68.67,1.71,1.71,0,0,1-1.08.35,1.19,1.19,0,0,1-.78-.23.8.8,0,0,1-.22-.72c0-.25.15-1.25.4-3,.14-.93.32-2.16.52-3.7l-1-.35.09-.52,2.18-.36.34.17-1,7.22Zm-.07-9.46a.85.85,0,0,1-.23-.6,1.12,1.12,0,0,1,.3-.78.94.94,0,0,1,.71-.32.79.79,0,0,1,.61.24.78.78,0,0,1,.24.57,1.16,1.16,0,0,1-.3.81,1,1,0,0,1-.76.33.75.75,0,0,1-.57-.25"/><path class="cls-2" d="M282,48.73a3.09,3.09,0,0,1,1.73-.56,1.65,1.65,0,0,1,1.32.52,2.54,2.54,0,0,1,.46,1.7,15.09,15.09,0,0,1-.33,2.35l-.07.36-.12.73a11.6,11.6,0,0,0-.24,1.86c0,.28.06.42.19.42a1.22,1.22,0,0,0,.73-.39l.18.4a1.77,1.77,0,0,1-.32.36,3.21,3.21,0,0,1-.61.39,1.86,1.86,0,0,1-.79.17c-.64,0-1-.31-1-.93a13.42,13.42,0,0,1,.28-1.88l.14-.73.06-.37c.1-.56.18-1,.25-1.45a8.17,8.17,0,0,0,.09-1.16,1.67,1.67,0,0,0-.21-1,.87.87,0,0,0-.73-.27,2.31,2.31,0,0,0-1.37.61,5.58,5.58,0,0,0-1.3,1.47l-.75,5.54H278.2l1-7.43-.75-.37.12-.58,1.87-.34.33.17-.2,1.84A5.85,5.85,0,0,1,282,48.73"/><path class="cls-2" d="M292.42,56.54a3.75,3.75,0,0,1-1.95.52,3,3,0,0,1-1.71-.47,2.7,2.7,0,0,1-1-1.23,4.19,4.19,0,0,1-.32-1.63A6.35,6.35,0,0,1,288,51a5.17,5.17,0,0,1,1.63-2,3.7,3.7,0,0,1,2.29-.77,2.32,2.32,0,0,1,1.65.52,1.82,1.82,0,0,1,.55,1.37,2.34,2.34,0,0,1-.89,1.84A5.79,5.79,0,0,1,291.17,53a8,8,0,0,1-2.15.4,3.51,3.51,0,0,0,.37,1.87,1.48,1.48,0,0,0,1.4.79,3.18,3.18,0,0,0,1.35-.32,3.75,3.75,0,0,0,1.21-.9l.34.57a4,4,0,0,1-1.27,1.11m-2.11-7a4.25,4.25,0,0,0-.87,1.45,6.25,6.25,0,0,0-.39,1.69,5.44,5.44,0,0,0,1.63-.33,4.05,4.05,0,0,0,1.4-.87,1.76,1.76,0,0,0,.57-1.28,1.33,1.33,0,0,0-.29-.92,1,1,0,0,0-.77-.31,1.74,1.74,0,0,0-1.28.57"/></g></g> </svg> </a> </div> <div class='global-nav-nap-menu' id="header-large"> <div class="dropdown" id="sitelinks-mobile"> <button class="btn btn-secondary dropdown-toggle" type="button" id="dropdownMenuButton" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"> <span class="hidden-xxs">Navigate to</span> </button> <div class="dropdown-menu" aria-labelledby="dropdownMenuButton"> <a class="dropdown-item" href="/content/help">Help</a> <a class="dropdown-item" href="/content/help-with-ordering">Ordering Information</a> <a class="dropdown-item" href="/new" >New Releases</a> <a class="dropdown-item" href="/author">Browse by Division</a> <a class="dropdown-item" href="/topic" class="site-links"> Browse by Topic</a> </div> </div> <ul class="user-links"> <li class="dropdown nap-mega-menu mega-dropdown"> <a href="#" class="dropdown-toggle" data-toggle="dropdown"><span class="icon-menu" data-icon=""> </span> Browse <span class="caret"></span></a> <ul class="dropdown-menu mega-dropdown-menu row" id="nap-mega-menu-inner"> <li class="d-flex" > <ul class="browse-col" > <li class="dropdown-header"><a href="/author">Publications by Division</a></li> <li><a href="/author/DBASSE/">Division of Behavioral and Social Sciences and Education</a> </li> <li><a href="/author/DELS/">Division on Earth and Life Studies</a></li> <li><a href="/author/DEPS/">Division on Engineering and Physical Sciences</a> </li> <li><a href="/author/GRP/">Gulf Research Program</a></li> <li><a href="/author/HMD/">Health and Medicine Division</a></li> <li><a href="/author/PGA/">Policy and Global Affairs</a></li> <li><a href="/author/TRB/">Transportation Research Board</a></li> <li><hr style="margin-left: 21px; margin-right: 20px;"></li> <li><a href="/author/NAS">National Academy of Sciences</a></li> <li><a href="/author/NAE">National Academy of Engineering</a></li> <li><a href="/author/NAM">National Academy of Medicine</a></li> </ul> <ul class="browse-col" > <li class="dropdown-header"><a href="/topic">Publications by Topic</a></li> <li><a href="/topic/276">Agriculture</a></li> <li><a href="/topic/277">Behavioral and Social Sciences</a></li> <li><a href="/topic/292">Biography and Autobiography</a></li> <li><a href="/topic/278">Biology and Life Sciences</a></li> <li><a href="/topic/279">Computers and Information Technology</a></li> <li><a href="/topic/280">Conflict and Security Issues</a></li> <li><a href="/topic/281">Earth Sciences</a></li> <li><a href="/topic/282">Education</a></li> <li><a href="/topic/283">Energy and Energy Conservation</a></li> <li><a href="/topic/284">Engineering and Technology</a></li> </ul> <ul class="browse-col"> <li><br> </li> <li><a href="/topic/285">Environment and Environmental Studies</a></li> <li><a href="/topic/287">Food and Nutrition</a></li> <li><a href="/topic/288">Health and Medicine</a></li> <li><a href="/topic/289">Industry and Labor</a></li> <li><a href="/topic/290">Math, Chemistry, and Physics</a></li> <li><a href="/topic/423">Policy for Science and Technology</a></li> <li><a href="/topic/293">Space and Aeronautics</a></li> <li><a href="/topic/478">Surveys and Statistics</a></li> <li><a href="/topic/294">Transportation and Infrastructure</a></li> </ul> <ul class="browse-col vertical-divider"> <li class="dropdown-header"><br></li> <li><a href="/collection">Searchable Collections</a></li> <li><a href="/new">New Releases</a></li> </ul> </li> </ul> </li> <li class="dropdown"> <a class="dropdown-toggle" data-toggle="dropdown" href="#"><span class="icon-menu" data-icon=""> </span> MyNAP <span class="caret"></span></a> <ul class="dropdown-menu"> <li><a href="/login.php" class="userOff"><span class="icon-menu" data-icon=""> </span> Login</a></li> <li><a href="/login.php?action=new" class="register"><span class="icon-menu" data-icon=""> </span> Register</a></li> </ul> </li> <li class="naphelp"><a href="/content/help"><span class="icon-menu" data-icon=""> </span> HELP</a></li> <li> <a href="/cart/cart.php"> <span class="icon-menu" data-icon=""> </span> Cart </a> </li> </ul> </div> <div class="global-nav__menus"> <div class="global-nav__menus--upper"> <div class="global-nav__controls"> <div class="controls__social"></div> <button aria-label="Search" class="controls__search" onclick="toggleSearch()"><span class="search__label"> Search </span> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class=""> <path d="M13.8 21.6a7.8 7.8 0 110-15.6 7.8 7.8 0 010 15.6zm0-2a5.8 5.8 0 100-11.6 5.8 5.8 0 000 11.6z"></path> <path d="M17.899 19.325l1.414-1.414 4.322 4.322-1.414 1.414z"></path> </svg> </button> <button class="controls__menu"> Menu <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class=""> <path fill-rule="evenodd" d="M8 23h15v-2.5H8V23zm0-6.25h15v-2.5H8v2.5zM8 8v2.5h15V8H8z"></path> </svg> </button> <button class="controls__nav" onclick="toggleMenu(); myMenu(this)"> Global Menu <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class="menu-off"> <path fill-rule="evenodd" d="M8 23h15v-2.5H8V23zm0-6.25h15v-2.5H8v2.5zM8 8v2.5h15V8H8z"></path> </svg> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class="menu-on"><path fill-rule="evenodd" d="M20.728 8l1.818 1.818-5.455 5.455 5.455 5.455-1.818 1.818-5.455-5.455-5.455 5.455L8 20.728l5.455-5.455L8 9.818 9.818 8l5.455 5.455z"></path></svg> </button> </div> </div> <div class="global-nav__menus--lower" > <nav role="navigation" class="global-nav__links " > <ul role="menu"> <li role="none" class="has-dropdown"><a href="https://www.nationalacademies.org/about" target="_self" role="menuitem" class="global-nav__link"><span> About Us </span></a> <div class="global-nav__dropdown"> <div class="dropdown__left"> <ul class="global-nav__links-widget" type="nas-nav-links-widget"> <li><a rel="" title="" href="https://www.nationalacademies.org/about" target="_self"> About Us </a></li> <li><a rel="" title="" href="https://www.nationalacademies.org/about/organization" target="_self"> Our Program Divisions </a></li> <li><a rel="" title="" href="https://www.nationalacademies.org/about/the-national-academies" target="_self"> Our Three Academies </a></li> <li><a rel="" title="" href="https://www.nationalacademies.org/about/leadership" target="_self"> Leadership </a></li> <li><a rel="" title="" href="https://www.nationalacademies.org/newsroom" target="_self"> Newsroom </a></li> <li><a rel="" title="" href="https://www.nationalacademies.org/ocga" target="_self"> Government Affairs </a></li> <li><a rel="" title="" href="https://www.nationalacademies.org/giving" target="_self"> Giving </a></li> <li><a rel="" title="" href="https://www.nationalacademies.org/about/institutional-policies-and-procedures/statement-on-diversity-and-inclusion" target="_self"> Statement on Diversity and Inclusion </a></li> </ul> </div> <div class="dropdown__right"> <p> <p>The National Academies of Sciences, Engineering, and Medicine are private, nonprofit institutions that provide expert advice on some of the most pressing challenges facing the nation and world. Our work helps shape sound policies, inform public opinion, and advance the pursuit of science, engineering, and medicine.</p> </p> <a rel="" title="Learn More" href="https://www.nationalacademies.org/about" target="_self" role="menuitem" class="button button--secondary button--outline button--icon"> Learn More <span class="button__icon"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class="w2 h2"> <path d="M17.885 10.708a1 1 0 111.412-1.416l5.624 5.608-5.616 5.732a1 1 0 11-1.428-1.4l4.228-4.316-4.22-4.208z"></path> <path d="M23.07 14a1 1 0 010 2H7a1 1 0 010-2h16.07z"></path> </svg> </span></a></div> </div> </li> <li role="none" class="has-dropdown"><a href="https://www.nationalacademies.org/events" target="_self" role="menuitem" class="global-nav__link"><span> Events </span></a> <div class="global-nav__dropdown"> <div class="dropdown__left"><span class="dropdown__left--default"><img src="https://nasemoceprodcomm-nationalacademies.cec.ocp.oraclecloud.com/content/published/api/v1.1/assets/CONTC88C4C0CA7CE4E7FA8630DEF6E1B3A8F/native/NAS+Building.jpg?cb=_cache_a061&channelToken=d2dc71410b56f1d61406108f1738d0f4" alt=""></span></div> <div class="dropdown__right"> <p> <p>Throughout any given year, the National Academies convene hundreds of conferences, workshops, symposia, forums, roundtables, and other gatherings that attract the finest minds in academia and the public and private sectors. These venues for discussion and debate are essential for allowing the scientific process to unfold.</p> </p> <a rel="" title="See All Events" href="https://www.nationalacademies.org/events" target="_self" role="menuitem" class="button button--secondary button--outline button--icon"> See All Events <span class="button__icon"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class="w2 h2"> <path d="M17.885 10.708a1 1 0 111.412-1.416l5.624 5.608-5.616 5.732a1 1 0 11-1.428-1.4l4.228-4.316-4.22-4.208z"></path> <path d="M23.07 14a1 1 0 010 2H7a1 1 0 010-2h16.07z"></path> </svg> </span></a></div> </div> </li> <li role="none" class="has-dropdown"><a href="https://www.nationalacademies.org/our-work" target="_self" role="menuitem" class="global-nav__link"><span> Our Work </span></a> <div class="global-nav__dropdown"> <div class="dropdown__left"> <ul class="global-nav__links-widget" type="nas-nav-links-widget"> <li><a rel="" title="" href="https://www.nationalacademies.org/our-work" target="_self"> Our Work </a></li> <li><a rel="" title="" href="https://www.nationalacademies.org/about/our-study-process" target="_self"> Our Study Process </a></li> <li><a rel="" title="" href="https://www.nationalacademies.org/about/institutional-policies-and-procedures/conflict-of-interest-policies-and-procedures" target="_self"> Conflict of Interest Policies and Procedures </a></li> <li><a rel="" title="" href="https://www.nationalacademies.org/about/institutional-policies-and-procedures/project-comments-and-information" target="_self"> Project Comments and Information </a></li> </ul> </div> <div class="dropdown__right"> <p> <p>The National Academies of Sciences, Engineering, and Medicine are the nation's pre-eminent source of high-quality, objective advice on science, engineering, and health matters. <br> <br> Top experts participate in our projects, activities, and studies to examine and assemble evidence-based findings to address some of society's greatest challenges.</p> </p> <a rel="" title="Learn More" href="https://www.nationalacademies.org/our-work" target="_self" role="menuitem" class="button button--secondary button--outline button--icon"> Learn More <span class="button__icon"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class="w2 h2"> <path d="M17.885 10.708a1 1 0 111.412-1.416l5.624 5.608-5.616 5.732a1 1 0 11-1.428-1.4l4.228-4.316-4.22-4.208z"></path> <path d="M23.07 14a1 1 0 010 2H7a1 1 0 010-2h16.07z"></path> </svg> </span></a></div> </div> </li> <li role="none" class="has-dropdown"><a href="https://www.nationalacademies.org/publications" target="_self" role="menuitem" class="global-nav__link"><span> Publications </span></a> <div class="global-nav__dropdown"> <div class="dropdown__left"> <ul class="global-nav__links-widget" loadchildren="true" type="nas-nav-links-widget"> <li><a rel="" title="" href="https://nap.nationalacademies.org/" target="_self"> Read Our Expert Reports and Published Proceedings </a></li> <li><a rel="" title="" href="https://www.pnas.org/" target="_self"> Explore PNAS, the Flagship Scientific Journal of NAS </a></li> <li><a rel="" title="" href="http://pubsindex.trb.org/" target="_self"> Access Transportation Research Board Publications </a></li> </ul> </div> <div class="dropdown__right"> <p>Our peer-reviewed reports present the evidence-based consensus of committees of experts. Published proceedings record the presentations and discussions that take place at hundreds of conferences, workshops, symposia, forums, roundtables, and other gatherings every year. And, our prestigious journals publish the latest scientific findings on a wide range of topics.</p> <a rel="" title="Learn More" href="https://www.nationalacademies.org/publications" target="_self" role="menuitem" class="button button--secondary button--outline button--icon"> Learn More <span class="button__icon"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class="w2 h2"> <path d="M17.885 10.708a1 1 0 111.412-1.416l5.624 5.608-5.616 5.732a1 1 0 11-1.428-1.4l4.228-4.316-4.22-4.208z"></path> <path d="M23.07 14a1 1 0 010 2H7a1 1 0 010-2h16.07z"></path> </svg> </span></a></div> </div> </li> <li role="none" class="has-dropdown"><a href="https://www.nationalacademies.org/topics" target="_self" role="menuitem" class="global-nav__link"><span> Topics </span></a> <div class="global-nav__dropdown"> <div class="dropdown__left"> <ul class="global-nav__links-widget" type="nas-nav-links-widget"> <li><a rel="" title="" href="https://www.nationalacademies.org/topics/covid-19-resources" target="_self"> Coronavirus Disease 2019 (COVID-19) </a></li> <li><a rel="" title="" href="https://www.nationalacademies.org/topics/resources-on-diversity-equity-and-inclusion" target="_self"> Diversity, Equity, and Inclusion </a></li> <li><a rel="" title="" href="https://www.nationalacademies.org/topics/climate" target="_self"> Climate </a></li> <li><a rel="" title="" href="https://www.nationalacademies.org/topics/economic-recovery" target="_self"> Economic Recovery </a></li> </ul> </div> <div class="dropdown__right"> <p> <p>Discover what the National Academies are doing in various topic areas to strengthen the fields of science, engineering, and medicine and their capacity to contribute to the well-being of our nation and the world.</p> </p> <a rel="" title="See All Topics" href="https://www.nationalacademies.org/topics" target="_self" role="menuitem" class="button button--secondary button--outline button--icon"> See All Topics <span class="button__icon"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class="w2 h2"> <path d="M17.885 10.708a1 1 0 111.412-1.416l5.624 5.608-5.616 5.732a1 1 0 11-1.428-1.4l4.228-4.316-4.22-4.208z"></path> <path d="M23.07 14a1 1 0 010 2H7a1 1 0 010-2h16.07z"></path> </svg> </span></a></div> </div> </li> <li role="none" class="has-dropdown"><a href="https://www.nationalacademies.org/engagement" target="_self" role="menuitem" class="global-nav__link"><span> Engagement </span></a> <div class="global-nav__dropdown"> <div class="dropdown__left"><span class="dropdown__left--default"><img src="https://nasemoceprodcomm-nationalacademies.ocecdn.oraclecloud.com/content/published/api/v1.1/assets/CONTC267CED7812243AB86410D548C73D067/native/engagement-nav.jpg?cb=_cache_a061&channelToken=d2dc71410b56f1d61406108f1738d0f4" alt=""></span></div> <div class="dropdown__right"> <p> <p>A powerful way to foster appreciation for the impact of science and critical and innovative thinking is through art and the humanities. Learn more about the National Academies’ various programs designed to connect, engage, and inspire.</p> </p> <a rel="" title="Learn More" href="https://www.nationalacademies.org/engagement" target="_self" role="menuitem" class="button button--secondary button--outline button--icon"> Learn More <span class="button__icon"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class="w2 h2"> <path d="M17.885 10.708a1 1 0 111.412-1.416l5.624 5.608-5.616 5.732a1 1 0 11-1.428-1.4l4.228-4.316-4.22-4.208z"></path> <path d="M23.07 14a1 1 0 010 2H7a1 1 0 010-2h16.07z"></path> </svg> </span></a></div> </div> </li> <li role="none" class="has-dropdown"><a href="https://www.nationalacademies.org/opportunities" target="_self" role="menuitem" class="global-nav__link"><span> Opportunities </span></a> <div class="global-nav__dropdown"> <div class="dropdown__left"> <ul class="global-nav__links-widget" type="nas-nav-links-widget"> <li><a rel="" title="" href="https://www.nationalacademies.org/careers" target="_self"> Careers </a></li> <li><a rel="" title="" href="https://www.nationalacademies.org/fellowships-and-grants" target="_self"> Fellowships and Grants </a></li> <li><a rel="" title="" href="https://www.nationalacademies.org/about/volunteers" target="_self"> Volunteers </a></li> <li><a rel="" title="" href="https://www.nationalacademies.org/about/sponsors" target="_self"> Sponsors </a></li> <li><a rel="" title="" href="https://www.nationalacademies.org/about/members" target="_self"> Members </a></li> </ul> </div> <div class="dropdown__right"> <p>Make a real impact on the scientific, engineering, and health-related challenges facing society. Whether as a sponsor or donor, a member or volunteer, or an employee or fellow, you can make a difference.</p> <a rel="" title="Learn More" href="https://www.nationalacademies.org/opportunities" target="_self" role="menuitem" class="button button--secondary button--outline button--icon"> Learn More <span class="button__icon"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class="w2 h2"> <path d="M17.885 10.708a1 1 0 111.412-1.416l5.624 5.608-5.616 5.732a1 1 0 11-1.428-1.4l4.228-4.316-4.22-4.208z"></path> <path d="M23.07 14a1 1 0 010 2H7a1 1 0 010-2h16.07z"></path> </svg> </span></a></div> </div> </li> </ul> </nav> </div> </div> </div> </header> <a name="content"></a> <script> $(".controls__menu").click(function(){ $("#mobile-menu").toggle(); }); function toggleMenu() { var element = document.getElementById("lowerMenu"); element.classList.toggle("menu-is-hidden"); } function myMenu(x) { x.classList.toggle("invert"); } function toggleSearch() { var element = document.getElementById("lowerMenu"); element.classList.toggle("search-is-hidden"); } </script>  <script> var acc = document.getElementsByClassName("accordion"); var i; for (i = 0; i < acc.length; i++) { acc[i].addEventListener("click", function() { this.classList.toggle("active"); var panel = this.nextElementSibling; if (panel.style.maxHeight) { panel.style.maxHeight = null; } else { panel.style.maxHeight = panel.scrollHeight + "px"; } }); } </script> <section class="top-rows"> <div class="container"> <div class="row"> <div class="col-md-8"> <h1>National Academies Press</h1> <p class="page-header__description"><em>The National Academies Press (NAP) publishes the publications of the National Academies of Sciences, Engineering, and Medicine. NAP publishes more than 200 publications per year on a wide range of topics in science, engineering, and medicine, providing authoritative, independently researched information on important matters in science and health policy.</em></p> </div> </div>   <div id="myCarousel" class="carousel slide" data-target="#carousel"> <div class="carousel-inner">  <div class="carousel-item item active "> <img style="width:" src="/images/homeslider/emergencyprep-may23.jpg" alt="Emergency Preparedness Collection"> <div class="container" style="background: rgba(255, 255, 255, 0.5)"> <div class="carousel-caption"> <h1>Emergency Preparedness Collection</h1> <p>View publications that provide guidelines and targeted resources for all stakeholders in a disaster response.</p> <p> <a class="btn btn-lg btn-primary" href="https://nap.nationalacademies.org/collection/35/emergency-preparedness-disaster-management">Learn more <span class="button__icon"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class="w2 h2"> <path d="M17.885 10.708a1 1 0 111.412-1.416l5.624 5.608-5.616 5.732a1 1 0 11-1.428-1.4l4.228-4.316-4.22-4.208z"></path> <path d="M23.07 14a1 1 0 010 2H7a1 1 0 010-2h16.07z"></path> </svg> </span></a> </p> </div> </div> </div> <div class="carousel-item item "> <img style="width:" src="/images/homeslider/diversity-oct-20.jpg" alt="Diversity, Equity, and Inclusion Collection"> <div class="container" style="background: rgba(255, 255, 255, 0.5)"> <div class="carousel-caption"> <h1>Diversity, Equity, and Inclusion Collection</h1> <p>View publications that discuss the issues in diversity and how we can build an inclusive and equitable nation</p> <p> <a class="btn btn-lg btn-primary" href="https://www.nap.edu/collection/97/diversity-equity-and-inclusion">Learn more <span class="button__icon"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class="w2 h2"> <path d="M17.885 10.708a1 1 0 111.412-1.416l5.624 5.608-5.616 5.732a1 1 0 11-1.428-1.4l4.228-4.316-4.22-4.208z"></path> <path d="M23.07 14a1 1 0 010 2H7a1 1 0 010-2h16.07z"></path> </svg> </span></a> </p> </div> </div> </div> <div class="carousel-item item "> <img style="width:" src="/images/homeslider/climate-change-10-20.jpg" alt="Climate Change Collection"> <div class="container" style="background: rgba(255, 255, 255, 0.5)"> <div class="carousel-caption"> <h1>Climate Change Collection</h1> <p>This collection emphasizes the importance of 21st century choices regarding long-term climate stabilization through improving understanding of the causes and consequences of climate change</p> <p> <a class="btn btn-lg btn-primary" href="https://www.nap.edu/collection/34/climate-change">Learn more <span class="button__icon"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class="w2 h2"> <path d="M17.885 10.708a1 1 0 111.412-1.416l5.624 5.608-5.616 5.732a1 1 0 11-1.428-1.4l4.228-4.316-4.22-4.208z"></path> <path d="M23.07 14a1 1 0 010 2H7a1 1 0 010-2h16.07z"></path> </svg> </span></a> </p> </div> </div> </div> </div>  <a class="carousel-control-prev" href="#myCarousel" role="button" data-slide="prev" onclick="$(this).closest('.carousel').carousel('prev');"> <span><?xml version="1.0" encoding="UTF-8"?> <svg width="19px" height="12px" viewBox="0 0 19 12" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"> <title>arrow-prev</title> <g id="Page-1" stroke="none" stroke-width="1" fill="none" fill-rule="evenodd"> <g id="Artboard" transform="translate(-39.000000, -34.000000)" fill="#FFFFFF" fill-rule="nonzero"> <g id="arrow-prev" transform="translate(39.000000, 34.000000)"> <path d="M11.885,1.72025483 C11.6247129,1.46954283 11.5199499,1.09789905 11.6109739,0.748155581 C11.701998,0.398412115 11.9746449,0.124992872 12.3241295,0.032979783 C12.673614,-0.0590333056 13.0455527,0.0446780023 13.297,0.304254828 L18.921,5.91225483 L13.305,11.6442548 C13.0562097,11.9053794 12.6860828,12.0123009 12.3363714,11.9240704 C11.9866601,11.83584 11.7115556,11.5661297 11.6164181,11.2182339 C11.5212806,10.870338 11.6208527,10.4981667 11.877,10.2442548 L16.105,5.92825483 L11.885,1.72025483 L11.885,1.72025483 Z" id="Path"></path> <path d="M17.07,5.01225483 C17.6222847,5.01225483 18.07,5.45997008 18.07,6.01225483 C18.07,6.56453958 17.6222847,7.01225483 17.07,7.01225483 L1,7.01225483 C0.44771525,7.01225483 0,6.56453958 0,6.01225483 C0,5.45997008 0.44771525,5.01225483 1,5.01225483 L17.07,5.01225483 Z" id="Path"></path> </g> </g> </g> </svg> </span> </a> <a class="carousel-control-next" href="#myCarousel" role="button" data-slide="next" onclick="$(this).closest('.carousel').carousel('next');"> <?xml version="1.0" encoding="UTF-8"?> <svg width="19px" height="12px" viewBox="0 0 19 12" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"> <title>arrow-next</title> <g id="Page-1" stroke="none" stroke-width="1" fill="none" fill-rule="evenodd"> <g id="Artboard" transform="translate(-39.000000, -34.000000)" fill="#FFFFFF" fill-rule="nonzero"> <g id="arrow-next" transform="translate(39.000000, 34.000000)"> <path d="M11.885,1.72025483 C11.6247129,1.46954283 11.5199499,1.09789905 11.6109739,0.748155581 C11.701998,0.398412115 11.9746449,0.124992872 12.3241295,0.032979783 C12.673614,-0.0590333056 13.0455527,0.0446780023 13.297,0.304254828 L18.921,5.91225483 L13.305,11.6442548 C13.0562097,11.9053794 12.6860828,12.0123009 12.3363714,11.9240704 C11.9866601,11.83584 11.7115556,11.5661297 11.6164181,11.2182339 C11.5212806,10.870338 11.6208527,10.4981667 11.877,10.2442548 L16.105,5.92825483 L11.885,1.72025483 L11.885,1.72025483 Z" id="Path"></path> <path d="M17.07,5.01225483 C17.6222847,5.01225483 18.07,5.45997008 18.07,6.01225483 C18.07,6.56453958 17.6222847,7.01225483 17.07,7.01225483 L1,7.01225483 C0.44771525,7.01225483 0,6.56453958 0,6.01225483 C0,5.45997008 0.44771525,5.01225483 1,5.01225483 L17.07,5.01225483 Z" id="Path"></path> </g> </g> </g> </svg> </a> </div> </div> </div> </section> <section class="middle-rows"> <div class="container ft"> <div class="book-row row" data-title="Featured Titles"> <div class="col-md-10"> <h2 class="row-title ft"> Featured Titles </h2> </div> <div class="books-flex-row"> <div class="book-tile col-sm-2 col-xs-5 "> <div class="well"> <a class="book-cover" href="https://nap.nationalacademies.org/catalog/27820/ending-unequal-treatment-strategies-to-achieve-equitable-health-care-and" data-title="Ending Unequal Treatment: Strategies to Achieve Equitable Health Care and Optimal Health for All" data-alias="cover"> <div class="img-container"> <img class="img-responsive" src="https://nap.nationalacademies.org/cover/27820/200" alt="Cover Image: Ending Unequal Treatment"> </div> </a> <h4 class="truncate"><a class="book-title truncate" href="https://nap.nationalacademies.org/catalog/27820/ending-unequal-treatment-strategies-to-achieve-equitable-health-care-and" data-title="Ending Unequal Treatment: Strategies to Achieve Equitable Health Care and Optimal Health for All" data-alias="title">Ending Unequal Treatment: Strategies to Achieve Equitable Health Care and Optimal Health for All</a></h4> </div> </div> <div class="book-tile col-sm-2 col-xs-5 "> <div class="well"> <a class="book-cover" href="https://nap.nationalacademies.org/catalog/26859/equity-in-k-12-stem-education-framing-decisions-for-the" data-title="Equity in K-12 STEM Education: Framing Decisions for the Future" data-alias="cover"> <div class="img-container"> <div class="prepubbanner hidden-xs hidden-sm">Prepublication</div> <img class="img-responsive" src="https://nap.nationalacademies.org/cover/26859/200" alt="Cover Image: Equity in K-12 STEM Education"> </div> </a> <h4 class="truncate"><a class="book-title truncate" href="https://nap.nationalacademies.org/catalog/26859/equity-in-k-12-stem-education-framing-decisions-for-the" data-title="Equity in K-12 STEM Education: Framing Decisions for the Future" data-alias="title">Equity in K-12 STEM Education: Framing Decisions for the Future</a></h4> </div> </div> <div class="book-tile col-sm-2 col-xs-5 "> <div class="well"> <a class="book-cover" href="https://nap.nationalacademies.org/catalog/26894/foundational-research-gaps-and-future-directions-for-digital-twins" data-title="Foundational Research Gaps and Future Directions for Digital Twins" data-alias="cover"> <div class="img-container"> <img class="img-responsive" src="https://nap.nationalacademies.org/cover/26894/200" alt="Cover Image: Foundational Research Gaps and Future Directions for Digital Twins"> </div> </a> <h4 class="truncate"><a class="book-title truncate" href="https://nap.nationalacademies.org/catalog/26894/foundational-research-gaps-and-future-directions-for-digital-twins" data-title="Foundational Research Gaps and Future Directions for Digital Twins" data-alias="title">Foundational Research Gaps and Future Directions for Digital Twins</a></h4> </div> </div> <div class="book-tile col-sm-2 col-xs-5 "> <div class="well"> <a class="book-cover" href="https://nap.nationalacademies.org/catalog/27160/future-directions-for-southern-ocean-and-antarctic-nearshore-and-coastal-research" data-title="Future Directions for Southern Ocean and Antarctic Nearshore and Coastal Research" data-alias="cover"> <div class="img-container"> <img class="img-responsive" src="https://nap.nationalacademies.org/cover/27160/200" alt="Cover Image: Future Directions for Southern Ocean and Antarctic Nearshore and Coastal Research"> </div> </a> <h4 class="truncate"><a class="book-title truncate" href="https://nap.nationalacademies.org/catalog/27160/future-directions-for-southern-ocean-and-antarctic-nearshore-and-coastal-research" data-title="Future Directions for Southern Ocean and Antarctic Nearshore and Coastal Research" data-alias="title">Future Directions for Southern Ocean and Antarctic Nearshore and Coastal Research</a></h4> </div> </div> <div class="book-tile col-sm-2 col-xs-5 hidden-xs"> <div class="well"> <a class="book-cover" href="https://nap.nationalacademies.org/catalog/27396/social-media-and-adolescent-health" data-title="Social Media and Adolescent Health" data-alias="cover"> <div class="img-container"> <img class="img-responsive" src="https://nap.nationalacademies.org/cover/27396/200" alt="Cover Image: Social Media and Adolescent Health"> </div> </a> <h4 class="truncate"><a class="book-title truncate" href="https://nap.nationalacademies.org/catalog/27396/social-media-and-adolescent-health" data-title="Social Media and Adolescent Health" data-alias="title">Social Media and Adolescent Health</a></h4> </div> </div> </div> </div> <div class="book-row row" data-title="New Releases"> <div class="col-md-10"> <h2 class="row-title ft"> New Releases <a href="/new" class="nr-vm pull-right">more<span class="arrow"></span></a> </h2> </div> <div class="books-flex-row"> <div class="book-tile col-sm-2 col-xs-5 "> <div class="well"> <a class="book-cover" href="https://nap.nationalacademies.org/catalog/28837/implementing-data-governance-at-transportation-agencies-volume-1-implementation-guide" data-title="Implementing Data Governance at Transportation Agencies: Volume 1: Implementation Guide" data-alias="cover"> <div class="img-container"> <img class="img-responsive" src="https://nap.nationalacademies.org/cover/28837/200" alt="Cover Image: Implementing Data Governance at Transportation Agencies"> </div> </a> <h4 class="truncate"><a class="book-title truncate" href="https://nap.nationalacademies.org/catalog/28837/implementing-data-governance-at-transportation-agencies-volume-1-implementation-guide" data-title="Implementing Data Governance at Transportation Agencies: Volume 1: Implementation Guide" data-alias="title">Implementing Data Governance at Transportation Agencies: Volume 1: Implementation Guide</a></h4> </div> </div> <div class="book-tile col-sm-2 col-xs-5 "> <div class="well"> <a class="book-cover" href="https://nap.nationalacademies.org/catalog/28838/implementing-data-governance-at-transportation-agencies-volume-2-communications-guide" data-title="Implementing Data Governance at Transportation Agencies: Volume 2: Communications Guide" data-alias="cover"> <div class="img-container"> <img class="img-responsive" src="https://nap.nationalacademies.org/cover/28838/200" alt="Cover Image: Implementing Data Governance at Transportation Agencies"> </div> </a> <h4 class="truncate"><a class="book-title truncate" href="https://nap.nationalacademies.org/catalog/28838/implementing-data-governance-at-transportation-agencies-volume-2-communications-guide" data-title="Implementing Data Governance at Transportation Agencies: Volume 2: Communications Guide" data-alias="title">Implementing Data Governance at Transportation Agencies: Volume 2: Communications Guide</a></h4> </div> </div> <div class="book-tile col-sm-2 col-xs-5 "> <div class="well"> <a class="book-cover" href="https://nap.nationalacademies.org/catalog/27644/artificial-intelligence-and-the-future-of-work" data-title="Artificial Intelligence and the Future of Work" data-alias="cover"> <div class="img-container"> <div class="prepubbanner hidden-xs hidden-sm">Prepublication</div> <img class="img-responsive" src="https://nap.nationalacademies.org/cover/27644/200" alt="Cover Image: Artificial Intelligence and the Future of Work"> </div> </a> <h4 class="truncate"><a class="book-title truncate" href="https://nap.nationalacademies.org/catalog/27644/artificial-intelligence-and-the-future-of-work" data-title="Artificial Intelligence and the Future of Work" data-alias="title">Artificial Intelligence and the Future of Work</a></h4> </div> </div> <div class="book-tile col-sm-2 col-xs-5 "> <div class="well"> <a class="book-cover" href="https://nap.nationalacademies.org/catalog/28542/transitioning-to-net-zero-carbon-engineering-challenges-and-opportunities-proceedings" data-title="Transitioning to Net-Zero Carbon: Engineering Challenges and Opportunities: Proceedings of a Forum" data-alias="cover"> <div class="img-container"> <img class="img-responsive" src="https://nap.nationalacademies.org/cover/28542/200" alt="Cover Image: Transitioning to Net-Zero Carbon"> </div> </a> <h4 class="truncate"><a class="book-title truncate" href="https://nap.nationalacademies.org/catalog/28542/transitioning-to-net-zero-carbon-engineering-challenges-and-opportunities-proceedings" data-title="Transitioning to Net-Zero Carbon: Engineering Challenges and Opportunities: Proceedings of a Forum" data-alias="title">Transitioning to Net-Zero Carbon: Engineering Challenges and Opportunities: Proceedings of a Forum</a></h4> </div> </div> <div class="book-tile col-sm-2 col-xs-5 hidden-xs"> <div class="well"> <a class="book-cover" href="https://nap.nationalacademies.org/catalog/27950/scaling-and-sustaining-pre-k-12-stem-education-innovations-systemic" data-title="Scaling and Sustaining Pre-K-12 STEM Education Innovations: Systemic Challenges, Systemic Responses" data-alias="cover"> <div class="img-container"> <div class="prepubbanner hidden-xs hidden-sm">Prepublication</div> <img class="img-responsive" src="https://nap.nationalacademies.org/cover/27950/200" alt="Cover Image: Scaling and Sustaining Pre-K-12 STEM Education Innovations"> </div> </a> <h4 class="truncate"><a class="book-title truncate" href="https://nap.nationalacademies.org/catalog/27950/scaling-and-sustaining-pre-k-12-stem-education-innovations-systemic" data-title="Scaling and Sustaining Pre-K-12 STEM Education Innovations: Systemic Challenges, Systemic Responses" data-alias="title">Scaling and Sustaining Pre-K-12 STEM Education Innovations: Systemic Challenges, Systemic Responses</a></h4> </div> </div> </div> </div> <div class="book-row row" data-title="Most Downloaded"> <div class="col-md-10"> <h2 class="row-title ft"> Most Downloaded <small>(last 7 days)</small> <a href="/most-downloaded" class="nr-vm pull-right">more<span class="arrow"></span></a> </h2> </div> <div class="books-flex-row"> <div class="book-tile col-sm-2 col-xs-5 "> <div class="well"> <a class="book-cover" href="https://nap.nationalacademies.org/catalog/25841/nutrition-during-pregnancy-and-lactation-exploring-new-evidence-proceedings-of" data-title="Nutrition During Pregnancy and Lactation: Exploring New Evidence: Proceedings of a Workshop" data-alias="cover"> <div class="img-container"> <img class="img-responsive" src="https://nap.nationalacademies.org/cover/25841/200" alt="Cover Image: Nutrition During Pregnancy and Lactation"> </div> </a> <h4 class="truncate"><a class="book-title truncate" href="https://nap.nationalacademies.org/catalog/25841/nutrition-during-pregnancy-and-lactation-exploring-new-evidence-proceedings-of" data-title="Nutrition During Pregnancy and Lactation: Exploring New Evidence: Proceedings of a Workshop" data-alias="title">Nutrition During Pregnancy and Lactation: Exploring New Evidence: Proceedings of a Workshop</a></h4> </div> </div> <div class="book-tile col-sm-2 col-xs-5 "> <div class="well"> <a class="book-cover" href="https://nap.nationalacademies.org/catalog/25858/reopening-k-12-schools-during-the-covid-19-pandemic-prioritizing" data-title="Reopening K-12 Schools During the COVID-19 Pandemic: Prioritizing Health, Equity, and Communities" data-alias="cover"> <div class="img-container"> <img class="img-responsive" src="https://nap.nationalacademies.org/cover/25858/200" alt="Cover Image: Reopening K-12 Schools During the COVID-19 Pandemic"> </div> </a> <h4 class="truncate"><a class="book-title truncate" href="https://nap.nationalacademies.org/catalog/25858/reopening-k-12-schools-during-the-covid-19-pandemic-prioritizing" data-title="Reopening K-12 Schools During the COVID-19 Pandemic: Prioritizing Health, Equity, and Communities" data-alias="title">Reopening K-12 Schools During the COVID-19 Pandemic: Prioritizing Health, Equity, and Communities</a></h4> </div> </div> <div class="book-tile col-sm-2 col-xs-5 "> <div class="well"> <a class="book-cover" href="https://nap.nationalacademies.org/catalog/25890/rapid-expert-consultation-on-staffing-considerations-for-crisis-standards-of-care-for-the-covid-19-pandemic-july-28-2020" data-title="Rapid Expert Consultation on Staffing Considerations for Crisis Standards of Care for the COVID-19 Pandemic (July 28, 2020)" data-alias="cover"> <div class="img-container"> <img class="img-responsive" src="https://nap.nationalacademies.org/cover/25890/200" alt="Cover Image: Rapid Expert Consultation on Staffing Considerations for Crisis Standards of Care for the COVID-19 Pandemic (July 28, 2020)"> </div> </a> <h4 class="truncate"><a class="book-title truncate" href="https://nap.nationalacademies.org/catalog/25890/rapid-expert-consultation-on-staffing-considerations-for-crisis-standards-of-care-for-the-covid-19-pandemic-july-28-2020" data-title="Rapid Expert Consultation on Staffing Considerations for Crisis Standards of Care for the COVID-19 Pandemic (July 28, 2020)" data-alias="title">Rapid Expert Consultation on Staffing Considerations for Crisis Standards of Care for the COVID-19 Pandemic (July 28, 2020)</a></h4> </div> </div> <div class="book-tile col-sm-2 col-xs-5 "> <div class="well"> <a class="book-cover" href="https://nap.nationalacademies.org/catalog/25761/a-vision-for-nsf-earth-sciences-2020-2030-earth-in" data-title="A Vision for NSF Earth Sciences 2020-2030: Earth in Time" data-alias="cover"> <div class="img-container"> <img class="img-responsive" src="https://nap.nationalacademies.org/cover/25761/200" alt="Cover Image: A Vision for NSF Earth Sciences 2020-2030"> </div> </a> <h4 class="truncate"><a class="book-title truncate" href="https://nap.nationalacademies.org/catalog/25761/a-vision-for-nsf-earth-sciences-2020-2030-earth-in" data-title="A Vision for NSF Earth Sciences 2020-2030: Earth in Time" data-alias="title">A Vision for NSF Earth Sciences 2020-2030: Earth in Time</a></h4> </div> </div> <div class="book-tile col-sm-2 col-xs-5 hidden-xs"> <div class="well"> <a class="book-cover" href="https://nap.nationalacademies.org/catalog/13165/a-framework-for-k-12-science-education-practices-crosscutting-concepts" data-title="A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas" data-alias="cover"> <div class="img-container"> <img class="img-responsive" src="https://nap.nationalacademies.org/cover/13165/200" alt="Cover Image: A Framework for K-12 Science Education"> </div> </a> <h4 class="truncate"><a class="book-title truncate" href="https://nap.nationalacademies.org/catalog/13165/a-framework-for-k-12-science-education-practices-crosscutting-concepts" data-title="A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas" data-alias="title">A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas</a></h4> </div> </div> </div> </div> <div class="book-row row" data-title="From the Archives"> <div class="col-md-10"> <h2 class="row-title ft"> From the Archives </h2> </div> <div class="books-flex-row"> <div class="book-tile col-sm-2 col-xs-5 "> <div class="well"> <a class="book-cover" href="https://nap.nationalacademies.org/catalog/18541/cooperation-and-competition-on-the-path-to-fusion-energy-a" data-title="Cooperation and Competition on the Path to Fusion Energy: A Report" data-alias="cover"> <div class="img-container"> <img class="img-responsive" src="https://nap.nationalacademies.org/cover/18541/200" alt="Cover Image: Cooperation and Competition on the Path to Fusion Energy"> </div> </a> <h4 class="truncate"><a class="book-title truncate" href="https://nap.nationalacademies.org/catalog/18541/cooperation-and-competition-on-the-path-to-fusion-energy-a" data-title="Cooperation and Competition on the Path to Fusion Energy: A Report" data-alias="title">Cooperation and Competition on the Path to Fusion Energy: A Report</a></h4> </div> </div> <div class="book-tile col-sm-2 col-xs-5 "> <div class="well"> <a class="book-cover" href="https://nap.nationalacademies.org/catalog/18933/great-lakes-water-quality-agreement-an-evolving-instrument-for-ecosystem" data-title="Great Lakes Water Quality Agreement: An Evolving Instrument for Ecosystem Management" data-alias="cover"> <div class="img-container"> <img class="img-responsive" src="https://nap.nationalacademies.org/cover/18933/200" alt="Cover Image: Great Lakes Water Quality Agreement"> </div> </a> <h4 class="truncate"><a class="book-title truncate" href="https://nap.nationalacademies.org/catalog/18933/great-lakes-water-quality-agreement-an-evolving-instrument-for-ecosystem" data-title="Great Lakes Water Quality Agreement: An Evolving Instrument for Ecosystem Management" data-alias="title">Great Lakes Water Quality Agreement: An Evolving Instrument for Ecosystem Management</a></h4> </div> </div> <div class="book-tile col-sm-2 col-xs-5 "> <div class="well"> <a class="book-cover" href="https://nap.nationalacademies.org/catalog/20529/trends-in-usage-of-hafnium" data-title="Trends in Usage of Hafnium" data-alias="cover"> <div class="img-container"> <img class="img-responsive" src="https://nap.nationalacademies.org/cover/20529/200" alt="Cover Image: Trends in Usage of Hafnium"> </div> </a> <h4 class="truncate"><a class="book-title truncate" href="https://nap.nationalacademies.org/catalog/20529/trends-in-usage-of-hafnium" data-title="Trends in Usage of Hafnium" data-alias="title">Trends in Usage of Hafnium</a></h4> </div> </div> <div class="book-tile col-sm-2 col-xs-5 "> <div class="well"> <a class="book-cover" href="https://nap.nationalacademies.org/catalog/28688/radiochemistry-of-bismuth" data-title="Radiochemistry of Bismuth" data-alias="cover"> <div class="img-container"> <img class="img-responsive" src="https://nap.nationalacademies.org/cover/28688/200" alt="Cover Image: Radiochemistry of Bismuth"> </div> </a> <h4 class="truncate"><a class="book-title truncate" href="https://nap.nationalacademies.org/catalog/28688/radiochemistry-of-bismuth" data-title="Radiochemistry of Bismuth" data-alias="title">Radiochemistry of Bismuth</a></h4> </div> </div> <div class="book-tile col-sm-2 col-xs-5 hidden-xs"> <div class="well"> <a class="book-cover" href="https://nap.nationalacademies.org/catalog/20328/paleoanthropology-in-the-peoples-republic-of-china-a-trip-report" data-title="Paleoanthropology in the People's Republic of China: A Trip Report of the American Paleoanthropology Delegation : Submitted to the Committee on Scholarly Communication With the People's Republic of China" data-alias="cover"> <div class="img-container"> <img class="img-responsive" src="https://nap.nationalacademies.org/cover/20328/200" alt="Cover Image: Paleoanthropology in the People's Republic of China"> </div> </a> <h4 class="truncate"><a class="book-title truncate" href="https://nap.nationalacademies.org/catalog/20328/paleoanthropology-in-the-peoples-republic-of-china-a-trip-report" data-title="Paleoanthropology in the People's Republic of China: A Trip Report of the American Paleoanthropology Delegation : Submitted to the Committee on Scholarly Communication With the People's Republic of China" data-alias="title">Paleoanthropology in the People's Republic of China: A Trip Report of the American Paleoanthropology Delegation : Submitted to the Committee on Scholarly Communication With the People's Republic of China</a></h4> </div> </div> </div> </div> </div> </section> <section class="bottom-rows"> <div class="container sc">  <div class="sc-row row" data-title="Searchable Collections"> <div class="col-md-10"> <h2 class="sc row-title">Searchable Collections <a href="/collection" class="sc-more nr-vm pull-right">more<span class="arrow"></span></a></h2> </div> <div class="sc-tile col-sm-2 col-xs-5 col-sc "> <div class="sc-outer" style="background: #fff url(https://nap.nationalacademies.org/images/collections/94.png) no-repeat center 24px;" data-alias="image"> <div class="sc-inner"> <h4 class="sc" data-alias="title">Coronavirus Resources</h4> <p class="truncate sc-desc " data-alias="description">This collection is a compilation of our resources related to COVID-19. Our publications explore prevention, response, and recovery from pandemic infectious disease.</p> <p class="sc-link"><a href="https://nap.nationalacademies.org/collection/94/coronavirus-resources" data-alias="view all" data-title="Coronavirus Resources">View all titles</a></p> </div> </div> </div> <div class="sc-tile col-sm-2 col-xs-5 col-sc "> <div class="sc-outer" style="background: #fff url(https://nap.nationalacademies.org/images/collections/95.png) no-repeat center 24px;" data-alias="image"> <div class="sc-inner"> <h4 class="sc" data-alias="title">Crisis Standards of Care</h4> <p class="truncate sc-desc " data-alias="description">Public health disasters justify temporarily adjusting practice standards and/or shifting the balance of ethical concerns to emphasize the needs of the community rather than the needs of individuals. Our Crisis Standards of Care publications provide guidance for use by state and local public health officials and health-sector agencies and institutions in establishing and implementing standards of care that should apply in disaster situations.</p> <p class="sc-link"><a href="https://nap.nationalacademies.org/collection/95/crisis-standards-of-care" data-alias="view all" data-title="Crisis Standards of Care">View all titles</a></p> </div> </div> </div> <div class="sc-tile col-sm-2 col-xs-5 col-sc "> <div class="sc-outer" style="background: #fff url(https://nap.nationalacademies.org/images/collections/35.png) no-repeat center 24px;" data-alias="image"> <div class="sc-inner"> <h4 class="sc" data-alias="title">Emergency Preparedness / Disaster Management</h4> <p class="truncate sc-desc " data-alias="description">Even prepared communities can be overwhelmed in a state of state of emergency. This collection of reports provides guidelines and targeted resources for all stakeholders in a disaster response, including state and local governments, emergency medical services and health care centers. These reports also examine the improvement of emergency services in rural communities and recommends post-disaster public engagement practices. </p> <p class="sc-link"><a href="https://nap.nationalacademies.org/collection/35/emergency-preparedness-disaster-management" data-alias="view all" data-title="Emergency Preparedness / Disaster Management">View all titles</a></p> </div> </div> </div> <div class="sc-tile col-sm-2 col-xs-5 col-sc "> <div class="sc-outer" style="background: #fff url(https://nap.nationalacademies.org/images/collections/34.png) no-repeat center 24px;" data-alias="image"> <div class="sc-inner"> <h4 class="sc" data-alias="title">Climate Change</h4> <p class="truncate sc-desc " data-alias="description">Climate change is occurring, is caused largely by human activities, and poses significant risks for a broad range of human and natural systems. Human activities largely determine the evolution of the Earth's climate, which not only impact the next few decades, but the coming centuries and millennia. This collection emphasizes the importance of 21st century choices regarding long-term climate stabilization through improving understanding of the causes and consequences of climate change and expanding the options available to limit the magnitude of climate change.</p> <p class="sc-link"><a href="https://nap.nationalacademies.org/collection/34/climate-change" data-alias="view all" data-title="Climate Change">View all titles</a></p> </div> </div> </div> <div class="sc-tile col-sm-2 col-xs-5 col-sc hidden-xs"> <div class="sc-outer" style="background: #fff url(https://nap.nationalacademies.org/images/collections/37.png) no-repeat center 24px;" data-alias="image"> <div class="sc-inner"> <h4 class="sc" data-alias="title">Infectious Disease</h4> <p class="truncate sc-desc sc-desclast " data-alias="description">A quarter of deaths worldwide are caused by infectious organisms. As new infectious diseases are continuing to emerge in new locations around the globe, it is essential society understands the environmental, human health, and ecological impacts cause by infectious diseases. This collection provides an overview of infectious disease, including the biology, history, the future trends of widespread and harmful infections, and what we need to do individually, and as a society, to address this growing global challenge.</p> <p class="sc-link"><a href="https://nap.nationalacademies.org/collection/37/infectious-disease" data-alias="view all" data-title="Infectious Disease">View all titles</a></p> </div> </div> </div> </div> <div class="mm-row row" data-title="Featured Multimedia"> <div class="col-md-10"> <h2 class="mm row-title">Featured Multimedia </h2> </div> <div class="mm-tile col-md-2 col-xs-5 col-mm "> <div class="mm-outer"> <div class="mm-inner"> <a href="https://www.nap.edu/visualizations/integration-of-immigrants/" class="mm-tile-image nonvideo" data-alias="thumbnail" data-title="Ten Things You Probably Didn't Know About Immigrants"> <img class="img-responsive mm" src="/images/video_thumbs/mm-immigrants-vis.png" alt="Infographic: Ten Things You Probably Didn't Know About Immigrants"> </a> </div> <h6 class="mm-type">Infographic</h6> <p class="truncate mm-desc "> <a href="https://www.nap.edu/visualizations/integration-of-immigrants/" class="mm-link" data-alias="title" data-title="Ten Things You Probably Didn't Know About Immigrants">Ten Things You Probably Didn't Know About Immigrants</a> </p> </div> </div> <div class="mm-tile col-md-2 col-xs-5 col-mm "> <div class="mm-outer"> <div class="mm-inner"> <a href="http://www.nap.edu/catalog.php?record_id=18358#resources" class="mm-tile-image video" data-alias="thumbnail" data-title="Confronting Commercial Sexual Exploitation and Sex Trafficking of Minors in the United States"><span class="play"></span> <img class="img-responsive mm" src="/images/video_thumbs/mm-18358.jpg" alt="Video: Confronting Commercial Sexual Exploitation and Sex Trafficking of Minors in the United States"> </a> </div> <h6 class="mm-type">Video</h6> <p class="truncate mm-desc "> <a href="http://www.nap.edu/catalog.php?record_id=18358#resources" class="mm-link" data-alias="title" data-title="Confronting Commercial Sexual Exploitation and Sex Trafficking of Minors in the United States">Confronting Commercial Sexual Exploitation and Sex Trafficking of Minors in the United States</a> </p> </div> </div> <div class="mm-tile col-md-2 col-xs-5 col-mm "> <div class="mm-outer"> <div class="mm-inner"> <a href="https://www.youtube.com/watch?v=VDy-IWfC4fQ" class="mm-tile-image video" data-alias="thumbnail" data-title="Bullying: Through a Teacher's Eyes"><span class="play"></span> <img class="img-responsive mm" src="/images/video_thumbs/mm-23482.jpg" alt="Video: Bullying: Through a Teacher's Eyes"> </a> </div> <h6 class="mm-type">Video</h6> <p class="truncate mm-desc "> <a href="https://www.youtube.com/watch?v=VDy-IWfC4fQ" class="mm-link" data-alias="title" data-title="Bullying: Through a Teacher's Eyes">Bullying: Through a Teacher's Eyes</a> </p> </div> </div> <div class="mm-tile col-md-2 col-xs-5 col-mm "> <div class="mm-outer"> <div class="mm-inner"> <a href="http://www.nap.edu/catalog.php?record_id=18373#resources" class="mm-tile-image video" data-alias="thumbnail" data-title="Abrupt Impacts of Climate Change"><span class="play"></span> <img class="img-responsive mm" src="/images/video_thumbs/mm-18373.jpg" alt="Video: Abrupt Impacts of Climate Change"> </a> </div> <h6 class="mm-type">Video</h6> <p class="truncate mm-desc "> <a href="http://www.nap.edu/catalog.php?record_id=18373#resources" class="mm-link" data-alias="title" data-title="Abrupt Impacts of Climate Change">Abrupt Impacts of Climate Change</a> </p> </div> </div> <div class="mm-tile col-md-2 col-xs-5 col-mm hidden-sm hidden-xs"> <div class="mm-outer"> <div class="mm-inner"> <a href="http://www.nap.edu/catalog.php?record_id=12192#resources" class="mm-tile-image video" data-alias="thumbnail" data-title="On Being a Scientist"><span class="play"></span> <img class="img-responsive mm" src="/images/video_thumbs/mm-12192.jpg" alt="Video: On Being a Scientist"> </a> </div> <h6 class="mm-type">Video</h6> <p class="truncate mm-desc mm-desclast"> <a href="http://www.nap.edu/catalog.php?record_id=12192#resources" class="mm-link" data-alias="title" data-title="On Being a Scientist">On Being a Scientist</a> </p> </div> </div> </div> </div> </section> <div id="bbt-sidebar"> <h3 class="bbt-hdr"> <span class="bbtclose pull-right"><a href="#" class="close">×</a></span>BROWSE BY TOPIC </h3> <nav id="bbt-sidebar-inner"> <ul> <li> <a href="/topic/276" tabindex="0" id="topic-Agriculture"><svg class="topic-icon topic-276" role="img" aria-labelledby="topic-276"><title id="topic-276">Agriculture</title><use xlink:href="/images/topics/svg/svgdefs.svg#topic-276"></use></svg> Agriculture </a> </li> <li> <a href="/topic/277" tabindex="0" id="topic-Behavioral and Social Sciences"><svg class="topic-icon topic-277" role="img" aria-labelledby="topic-277"><title id="topic-277">Behavioral and Social Sciences</title><use xlink:href="/images/topics/svg/svgdefs.svg#topic-277"></use></svg> Behavioral and Social Sciences </a> </li> <li> <a href="/topic/292" tabindex="0" id="topic-Biography and Autobiography"><svg class="topic-icon topic-292" role="img" aria-labelledby="topic-292"><title id="topic-292">Biography and Autobiography</title><use xlink:href="/images/topics/svg/svgdefs.svg#topic-292"></use></svg> Biography and Autobiography </a> </li> <li> <a href="/topic/278" tabindex="0" id="topic-Biology and Life Sciences"><svg class="topic-icon topic-278" role="img" aria-labelledby="topic-278"><title id="topic-278">Biology and Life Sciences</title><use xlink:href="/images/topics/svg/svgdefs.svg#topic-278"></use></svg> Biology and Life Sciences </a> </li> <li> <a href="/topic/279" tabindex="0" id="topic-Computers and Information Technology"><svg class="topic-icon topic-279" role="img" aria-labelledby="topic-279"><title id="topic-279">Computers and Information Technology</title><use xlink:href="/images/topics/svg/svgdefs.svg#topic-279"></use></svg> Computers and Information Technology </a> </li> <li> <a href="/topic/280" tabindex="0" id="topic-Conflict and Security Issues"><svg class="topic-icon topic-280" role="img" aria-labelledby="topic-280"><title id="topic-280">Conflict and Security Issues</title><use xlink:href="/images/topics/svg/svgdefs.svg#topic-280"></use></svg> Conflict and Security Issues </a> </li> <li> <a href="/topic/281" tabindex="0" id="topic-Earth Sciences"><svg class="topic-icon topic-281" role="img" aria-labelledby="topic-281"><title id="topic-281">Earth Sciences</title><use xlink:href="/images/topics/svg/svgdefs.svg#topic-281"></use></svg> Earth Sciences </a> </li> <li> <a href="/topic/282" tabindex="0" id="topic-Education"><svg class="topic-icon topic-282" role="img" aria-labelledby="topic-282"><title id="topic-282">Education</title><use xlink:href="/images/topics/svg/svgdefs.svg#topic-282"></use></svg> Education </a> </li> <li> <a href="/topic/283" tabindex="0" id="topic-Energy and Energy Conservation"><svg class="topic-icon topic-283" role="img" aria-labelledby="topic-283"><title id="topic-283">Energy and Energy Conservation</title><use xlink:href="/images/topics/svg/svgdefs.svg#topic-283"></use></svg> Energy and Energy Conservation </a> </li> <li> <a href="/topic/284" tabindex="0" id="topic-Engineering and Technology"><svg class="topic-icon topic-284" role="img" aria-labelledby="topic-284"><title id="topic-284">Engineering and Technology</title><use xlink:href="/images/topics/svg/svgdefs.svg#topic-284"></use></svg> Engineering and Technology </a> </li> <li> <a href="/topic/285" tabindex="0" id="topic-Environment and Environmental Studies"><svg class="topic-icon topic-285" role="img" aria-labelledby="topic-285"><title id="topic-285">Environment and Environmental Studies</title><use xlink:href="/images/topics/svg/svgdefs.svg#topic-285"></use></svg> Environment and Environmental Studies </a> </li> <li> <a href="/topic/287" tabindex="0" id="topic-Food and Nutrition"><svg class="topic-icon topic-287" role="img" aria-labelledby="topic-287"><title id="topic-287">Food and Nutrition</title><use xlink:href="/images/topics/svg/svgdefs.svg#topic-287"></use></svg> Food and Nutrition </a> </li> <li> <a href="/topic/288" tabindex="0" id="topic-Health and Medicine"><svg class="topic-icon topic-288" role="img" aria-labelledby="topic-288"><title id="topic-288">Health and Medicine</title><use xlink:href="/images/topics/svg/svgdefs.svg#topic-288"></use></svg> Health and Medicine </a> </li> <li> <a href="/topic/289" tabindex="0" id="topic-Industry and Labor"><svg class="topic-icon topic-289" role="img" aria-labelledby="topic-289"><title id="topic-289">Industry and Labor</title><use xlink:href="/images/topics/svg/svgdefs.svg#topic-289"></use></svg> Industry and Labor </a> </li> <li> <a href="/topic/290" tabindex="0" id="topic-Math, Chemistry, and Physics"><svg class="topic-icon topic-290" role="img" aria-labelledby="topic-290"><title id="topic-290">Math, Chemistry, and Physics</title><use xlink:href="/images/topics/svg/svgdefs.svg#topic-290"></use></svg> Math, Chemistry, and Physics </a> </li> <li> <a href="/topic/423" tabindex="0" id="topic-Policy for Science and Technology"><svg class="topic-icon topic-423" role="img" aria-labelledby="topic-423"><title id="topic-423">Policy for Science and Technology</title><use xlink:href="/images/topics/svg/svgdefs.svg#topic-423"></use></svg> Policy for Science and Technology </a> </li> <li> <a href="/topic/293" tabindex="0" id="topic-Space and Aeronautics"><svg class="topic-icon topic-293" role="img" aria-labelledby="topic-293"><title id="topic-293">Space and Aeronautics</title><use xlink:href="/images/topics/svg/svgdefs.svg#topic-293"></use></svg> Space and Aeronautics </a> </li> <li> <a href="/topic/478" tabindex="0" id="topic-Surveys and Statistics"><svg class="topic-icon topic-478" role="img" aria-labelledby="topic-478"><title id="topic-478">Surveys and Statistics</title><use xlink:href="/images/topics/svg/svgdefs.svg#topic-478"></use></svg> Surveys and Statistics </a> </li> <li> <a href="/topic/294" tabindex="0" id="topic-Transportation and Infrastructure"><svg class="topic-icon topic-294" role="img" aria-labelledby="topic-294"><title id="topic-294">Transportation and Infrastructure</title><use xlink:href="/images/topics/svg/svgdefs.svg#topic-294"></use></svg> Transportation and Infrastructure </a> </li> <li style="border-top: 1px solid #999;" class="visible-md visible-lg"> <a href="/academy-scope">Browse Topics in AcademyScope <img src="//nap.nationalacademies.org/images/icon_academyscope.png" class="topic-icon" style="border: none; height: auto; margin-top: 6px;" alt="Browse titles in AcademyScope"> </a> </li> </ul> </nav> </div> <div class="overlay"></div> <script> $('.bbt-btn').on('click', function() { $('#bbt-sidebar').animate({ width: 'toggle' }); $('.overlay').css('height', $(document).height()).fadeIn(); }); </script>  <footer class="global-footer" style="background: #211747; border-top: none" id="global-footer-nap"> <div class="container"> <div class="global-footer__orgs"> <div class="global-footer__logo"> <a href="https://nap.nationalacademies.org"><img src="/images/footer-nap-text.png" alt="National Academies Press: Washington, DC | Home" class="img-responsive"></a> </div> <div> <form id="subscribe-form" action="/updates/" method="POST"> <input type="hidden" name="action" value="subscribe"> <div class="input-group"> <label for="email" class="sr-only">Email Address</label> <input type="hidden" name="SOURCE" value="homepage"> <input class="subscribe-input form-control" type="text" name="EMAIL" id="email" placeholder="Sign up for e-mail updates" title="Enter your e-mail address to subscribe to updates from NAP."> <span class="subscribe-button"> <button type="submit" class="btn btn-subscribe">Subscribe</button> </span> </div> </form></div></div> <div class="global-footer__links"> <ul class="global-footer__nav"> <li> <h6>NAP Quick Links</h6> <ul> <li><a href="/">Home</a></li> <li><a href="/content/about-the-national-academies-press">About</a></li> <li><a href="https://notes.nap.edu/">Notes from NAP</a></li> </ul> <h6>Request A</h6> <ul> <li><a href="/content/request-desk-copies">Desk Copy</a> </li> <li><a href="/content/request/exam_copy.html">Exam Copy </a></li> <li><a href="/content/request-review-copies">Review Copy</a></li> <li><a href="/content/request-rights-and-permissions">Reprint Permission</a></li> </ul> </li> <li> <h6>Browse Publications</h6> <ul> <li><a href="/author">By Division</a></li> <li><a href="/new/">By New Releases</a></li> <li><a href="/collection">By Searchable Collections</a></li> <li><a href="/topic">By Topic</a></li> </ul> </li> <li> <h6>NAP Ordering</h6> <ul> <li><a href="/content/contact-customer-service">Contact Customer Service</a></li> </ul> <h6>Using NAP.edu</h6> <ul> <li><a href="/content/searching-nap-publications">Tips for Searching</a> </li> <li><a href="/content/using-mynap">Help With MyNAP</a></li> <li><a href="/content/about-pdfs">Downloading and Reading PDFs</a> </li> </ul> </li> <li> <h6>NAP Information</h6> <ul> <li><a href="/content/help-with-discounts">Discounts</a></li> <li><a href="/content/information-for-book-trade-customers">Book Trade Customers</a></li> <li><a href="/content/request-rights-and-permissions">Rights and Permissions</a></li> <li><a href="/content/international-ordering-and-distribution">International Ordering and Distribution</a></li> <li><a href="/content/translation-rights">Translation Rights</a></li> </ul></li> </ul> </div></div></footer>  <footer class="global-footer" style="background: #666; border-top: none"><div class="container"><div class="global-footer__orgs"><div class="global-footer__logo"> <a aria-label="Logo of The National Academies" href="https://www.nationalacademies.org/home"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 315.11 58.33"><defs><style>.cls-1{fill:#fff;}</style></defs><g id="Layer_2" data-name="Layer 2"><g id="Layer_1-2" data-name="Layer 1"><polygon class="cls-1" points="3.73 7.55 20.84 25.49 20.84 1.5 17.81 1.5 17.81 18.08 0.7 0.14 0.7 24.06 3.73 24.06 3.73 7.55"/><polygon class="cls-1" points="28.49 24.06 31.84 24.06 38.98 7.25 45.92 23.87 45.99 24.06 49.34 24.06 39.05 0 28.49 24.06"/><polygon class="cls-1" points="153.23 24.06 156.58 24.06 163.72 7.25 170.66 23.87 170.73 24.06 174.08 24.06 163.79 0 153.23 24.06"/><polygon class="cls-1" points="59.72 24.06 62.76 24.06 62.76 4.41 69.52 4.41 69.52 1.5 52.96 1.5 52.96 4.41 59.72 4.41 59.72 24.06"/><rect class="cls-1" x="78.85" y="1.5" width="3.03" height="22.55"/><path class="cls-1" d="M115.69,12.8a11.72,11.72,0,0,0-23.44,0,11.72,11.72,0,0,0,23.44,0m-3.09,0A8.63,8.63,0,1,1,104,4a8.7,8.7,0,0,1,8.63,8.76"/><polygon class="cls-1" points="128.29 7.55 145.4 25.49 145.4 1.5 142.37 1.5 142.37 18.08 125.25 0.14 125.25 24.06 128.29 24.06 128.29 7.55"/><polygon class="cls-1" points="184.65 1.5 181.62 1.5 181.62 24.06 193.7 24.06 193.7 21.16 184.65 21.16 184.65 1.5"/><path class="cls-1" d="M37.15,34.08A11.48,11.48,0,0,0,25.37,45.8,11.36,11.36,0,0,0,37,57.38a11.77,11.77,0,0,0,6.79-2.19l.13-.09V51.2l-.51.51A9.77,9.77,0,0,1,41,53.5a8.9,8.9,0,0,1-3.95,1A8.75,8.75,0,0,1,37,37a9.09,9.09,0,0,1,3.66.82,10.71,10.71,0,0,1,2.78,2l.51.5V36.4l-.12-.09a10.62,10.62,0,0,0-6.67-2.23"/><path class="cls-1" d="M91.91,37.08a12.19,12.19,0,0,0-8.29-2.64H78.85V57h4.74c3.72,0,6-.73,8.22-2.61a10.75,10.75,0,0,0,4-8.65,11,11,0,0,0-3.86-8.65m-2.09,15.1a9.11,9.11,0,0,1-6.1,1.91H81.88V37.34h1.84c5.44,0,9,3.29,9,8.39a8.09,8.09,0,0,1-2.85,6.45"/><polygon class="cls-1" points="104.99 56.99 118.4 56.99 118.4 54.09 108.02 54.09 108.02 46.16 117.11 46.16 117.11 43.26 108.02 43.26 108.02 37.34 118.4 37.34 118.4 34.44 104.99 34.44 104.99 56.99"/><polygon class="cls-1" points="176.17 56.99 189.58 56.99 189.58 54.09 179.2 54.09 179.2 46.16 188.28 46.16 188.28 43.26 179.2 43.26 179.2 37.34 189.58 37.34 189.58 34.44 176.17 34.44 176.17 56.99"/><polygon class="cls-1" points="138.88 51.34 130.31 32.49 126.44 56.99 129.55 56.99 131.62 42.47 138.84 58.33 146.15 42.47 148.13 56.99 151.23 56.99 147.61 32.45 138.88 51.34"/><rect class="cls-1" x="161.31" y="34.44" width="3.03" height="22.55"/><path class="cls-1" d="M209,46.15A10.78,10.78,0,0,0,205.49,44l-2.12-.92a6.8,6.8,0,0,1-2.21-1.33,2,2,0,0,1-.73-1.69A3.07,3.07,0,0,1,203.82,37a3.62,3.62,0,0,1,2.28.69,4.87,4.87,0,0,1,1.2,1.55l.15.3,2.45-1.62-.12-.24a7,7,0,0,0-2.24-2.55,6.34,6.34,0,0,0-3.69-1c-3.8,0-6.45,2.45-6.45,6a4.86,4.86,0,0,0,1.6,3.8,9.51,9.51,0,0,0,2.84,1.78l2.15,1a9.5,9.5,0,0,1,2.56,1.46,3,3,0,0,1,1,2.35,4.2,4.2,0,0,1-7.06,2.92,4.93,4.93,0,0,1-1.24-2.64l-.05-.33-3,.82.06.28a8.32,8.32,0,0,0,2.13,4,6.74,6.74,0,0,0,5,1.87,6.91,6.91,0,0,0,7.24-7A5.58,5.58,0,0,0,209,46.15"/><polygon class="cls-1" points="0 56.99 3.35 56.99 10.49 40.18 17.43 56.81 17.5 56.99 20.86 56.99 10.56 32.93 0 56.99"/><polygon class="cls-1" points="50.21 56.99 53.57 56.99 60.71 40.18 67.64 56.81 67.72 56.99 71.07 56.99 60.78 32.93 50.21 56.99"/><path class="cls-1" d="M233.74,2.1a3.34,3.34,0,0,0-.93-.11,2.53,2.53,0,0,0-1.52.45,1.48,1.48,0,0,0-.63,1.28,2,2,0,0,0,.54,1.44,7.94,7.94,0,0,0,1.64,1.26,13.5,13.5,0,0,1,1.26.89,3.76,3.76,0,0,1,.83,1,2.62,2.62,0,0,1,.33,1.33,3.06,3.06,0,0,1-.5,1.74,3.26,3.26,0,0,1-1.4,1.18,5.06,5.06,0,0,1-2.09.41,8.3,8.3,0,0,1-1.94-.22,3.51,3.51,0,0,1-1.24-.46l.34-2.18h.92l.09,1.62a2.53,2.53,0,0,0,.81.33,3.86,3.86,0,0,0,1,.13,2.93,2.93,0,0,0,1.77-.53,1.68,1.68,0,0,0,.73-1.47,1.91,1.91,0,0,0-.49-1.34,6.42,6.42,0,0,0-1.49-1.16c-.52-.34-1-.65-1.32-.94a3.76,3.76,0,0,1-.9-1,2.64,2.64,0,0,1-.37-1.4,2.64,2.64,0,0,1,.5-1.62,3.23,3.23,0,0,1,1.35-1.08,4.58,4.58,0,0,1,1.86-.37,7,7,0,0,1,1.72.18,3.31,3.31,0,0,1,1.09.45l-.35,2h-.83l-.12-1.47a2.39,2.39,0,0,0-.68-.3"/><path class="cls-1" d="M241,5a2,2,0,0,0-1.35.54,3.66,3.66,0,0,0-.92,1.52,7,7,0,0,0-.33,2.24,3.52,3.52,0,0,0,.43,1.95,1.39,1.39,0,0,0,1.24.66,2.38,2.38,0,0,0,1.1-.24,5.05,5.05,0,0,0,1-.72l.3.57a3.84,3.84,0,0,1-1.14.95,3.43,3.43,0,0,1-1.76.43,2.44,2.44,0,0,1-2-.91,4,4,0,0,1-.73-2.54A6.43,6.43,0,0,1,237.34,7a5.3,5.3,0,0,1,1.55-2.08,3.74,3.74,0,0,1,2.42-.83,5,5,0,0,1,.93.09,3.09,3.09,0,0,1,.81.26l-.42,1.49-.26-.09A2.53,2.53,0,0,0,241,5"/><path class="cls-1" d="M246.1,11.61a.56.56,0,0,0,.07.29.21.21,0,0,0,.18.1.65.65,0,0,0,.34-.11,2.64,2.64,0,0,0,.44-.35l.2.37a2.88,2.88,0,0,1-.68.67,1.71,1.71,0,0,1-1.08.35,1.14,1.14,0,0,1-.78-.23.8.8,0,0,1-.22-.72c0-.25.15-1.25.4-3,.14-.93.31-2.16.52-3.7l-1-.35.09-.52,2.18-.36.34.17-1,7.22ZM246,2.15a.84.84,0,0,1-.23-.59,1.13,1.13,0,0,1,.3-.79.94.94,0,0,1,.71-.32.79.79,0,0,1,.61.24.77.77,0,0,1,.23.57,1.15,1.15,0,0,1-.29.81,1,1,0,0,1-.77.33.75.75,0,0,1-.56-.25"/><path class="cls-1" d="M254,12.43a3.75,3.75,0,0,1-1.95.52,3,3,0,0,1-1.72-.47,2.74,2.74,0,0,1-1-1.23A4,4,0,0,1,249,9.62a6.35,6.35,0,0,1,.59-2.75,5.08,5.08,0,0,1,1.63-2,3.7,3.7,0,0,1,2.29-.77,2.27,2.27,0,0,1,1.64.52A1.79,1.79,0,0,1,255.72,6a2.34,2.34,0,0,1-.89,1.84,5.79,5.79,0,0,1-2.08,1.12,8.1,8.1,0,0,1-2.15.4,3.42,3.42,0,0,0,.37,1.87,1.48,1.48,0,0,0,1.4.79,3.18,3.18,0,0,0,1.35-.32,3.75,3.75,0,0,0,1.21-.9l.34.57A4,4,0,0,1,254,12.43m-2.11-7A4.1,4.1,0,0,0,251,6.88a5.9,5.9,0,0,0-.39,1.69,5.31,5.31,0,0,0,1.62-.33,4,4,0,0,0,1.41-.87,1.76,1.76,0,0,0,.57-1.28,1.33,1.33,0,0,0-.29-.92,1,1,0,0,0-.77-.31,1.74,1.74,0,0,0-1.28.57"/><path class="cls-1" d="M261.24,4.62A3.14,3.14,0,0,1,263,4.06a1.67,1.67,0,0,1,1.32.52,2.61,2.61,0,0,1,.46,1.71,15.44,15.44,0,0,1-.34,2.34l-.06.36-.13.74a11.51,11.51,0,0,0-.24,1.85c0,.28.06.42.2.42a1.22,1.22,0,0,0,.72-.39l.18.4a1.54,1.54,0,0,1-.32.36,2.92,2.92,0,0,1-.61.39,1.73,1.73,0,0,1-.79.17.84.84,0,0,1-1-.93,12.88,12.88,0,0,1,.27-1.88l.14-.73.06-.37c.1-.55.19-1,.25-1.45a8.17,8.17,0,0,0,.09-1.16,1.67,1.67,0,0,0-.21-1,.87.87,0,0,0-.73-.27,2.33,2.33,0,0,0-1.37.61,5.75,5.75,0,0,0-1.3,1.47l-.75,5.54h-1.46l1-7.43L257.62,5l.12-.58,1.88-.34.32.17-.2,1.84a5.72,5.72,0,0,1,1.5-1.45"/><path class="cls-1" d="M270.77,5a2,2,0,0,0-1.35.54,3.66,3.66,0,0,0-.92,1.52,7,7,0,0,0-.33,2.24,3.52,3.52,0,0,0,.43,1.95,1.39,1.39,0,0,0,1.24.66,2.38,2.38,0,0,0,1.1-.24,5.05,5.05,0,0,0,1-.72l.3.57a3.84,3.84,0,0,1-1.14.95,3.43,3.43,0,0,1-1.76.43,2.44,2.44,0,0,1-2-.91,4,4,0,0,1-.73-2.54A6.43,6.43,0,0,1,267.13,7a5.3,5.3,0,0,1,1.55-2.08,3.76,3.76,0,0,1,2.42-.83,5,5,0,0,1,.93.09,3,3,0,0,1,.81.26l-.42,1.49-.26-.09A2.53,2.53,0,0,0,270.77,5"/><path class="cls-1" d="M278.66,12.43a3.75,3.75,0,0,1-2,.52,3,3,0,0,1-1.71-.47,2.7,2.7,0,0,1-1-1.23,4.19,4.19,0,0,1-.32-1.63,6.35,6.35,0,0,1,.59-2.75,5.17,5.17,0,0,1,1.63-2,3.7,3.7,0,0,1,2.29-.77,2.32,2.32,0,0,1,1.65.52A1.82,1.82,0,0,1,280.38,6a2.34,2.34,0,0,1-.89,1.84,5.79,5.79,0,0,1-2.08,1.12,8,8,0,0,1-2.15.4,3.51,3.51,0,0,0,.37,1.87A1.48,1.48,0,0,0,277,12a3.18,3.18,0,0,0,1.35-.32,3.75,3.75,0,0,0,1.21-.9l.34.57a4,4,0,0,1-1.27,1.11m-2.11-7a4.25,4.25,0,0,0-.87,1.45,6.25,6.25,0,0,0-.39,1.69,5.44,5.44,0,0,0,1.63-.33,4.05,4.05,0,0,0,1.4-.87,1.76,1.76,0,0,0,.57-1.28,1.33,1.33,0,0,0-.29-.92,1,1,0,0,0-.77-.31,1.74,1.74,0,0,0-1.28.57"/><path class="cls-1" d="M286.18,5.13a2.75,2.75,0,0,0-1.09-.21,1.85,1.85,0,0,0-1.13.31,1,1,0,0,0-.43.89,1.43,1.43,0,0,0,.34.93,6.08,6.08,0,0,0,1,.88,10.43,10.43,0,0,1,.88.74,3.1,3.1,0,0,1,.6.76,2.15,2.15,0,0,1,.26,1.05,2.09,2.09,0,0,1-.9,1.81,3.71,3.71,0,0,1-2.22.64,6.32,6.32,0,0,1-1.37-.15,2.1,2.1,0,0,1-.9-.34l.24-1.06a3.41,3.41,0,0,0,.88.44,3.37,3.37,0,0,0,1.18.21,2.21,2.21,0,0,0,1.15-.29,1,1,0,0,0,.48-.92,1.37,1.37,0,0,0-.38-1,6.83,6.83,0,0,0-1.1-.89,3.07,3.07,0,0,1-1.58-2.5,2.16,2.16,0,0,1,.4-1.27,2.64,2.64,0,0,1,1.09-.84,3.81,3.81,0,0,1,1.54-.3,6.32,6.32,0,0,1,1.13.1,4.07,4.07,0,0,1,.8.19l-.26,1.17a1.55,1.55,0,0,0-.6-.39"/><polygon class="cls-1" points="229.34 23.43 236.61 23.43 236.51 25.87 235.6 25.87 235.35 24.25 231.87 24.13 231.29 28.48 234.85 28.36 234.74 29.51 231.21 29.38 230.58 34.05 234.91 33.87 235.77 32.01 236.63 32.18 236.01 34.84 227.85 34.84 227.91 34.24 229.06 34.05 230.29 24.25 229.24 24.09 229.34 23.43"/><path class="cls-1" d="M242.18,26.67a3.16,3.16,0,0,1,1.73-.56,1.67,1.67,0,0,1,1.32.53,2.51,2.51,0,0,1,.46,1.7,14.42,14.42,0,0,1-.34,2.35l-.06.35-.12.74a10.81,10.81,0,0,0-.25,1.86c0,.27.07.41.2.41a1.15,1.15,0,0,0,.72-.38l.19.4a1.54,1.54,0,0,1-.32.35,2.46,2.46,0,0,1-.61.39,1.76,1.76,0,0,1-.79.18c-.65,0-1-.31-1-.94a11.94,11.94,0,0,1,.28-1.87l.14-.74.06-.37c.1-.55.18-1,.24-1.45a8.14,8.14,0,0,0,.1-1.16,1.64,1.64,0,0,0-.21-1,.87.87,0,0,0-.73-.27,2.3,2.3,0,0,0-1.38.61,5.67,5.67,0,0,0-1.29,1.46l-.76,5.55h-1.45l1-7.44-.76-.36.13-.59,1.87-.34.32.17-.2,1.85a5.77,5.77,0,0,1,1.5-1.46"/><path class="cls-1" d="M252.77,37.29a4,4,0,0,1-1.55,1.05,5.36,5.36,0,0,1-1.78.32,5.69,5.69,0,0,1-1-.09,3.45,3.45,0,0,1-.76-.19l.32-1.24a5,5,0,0,0,.9.34,3.56,3.56,0,0,0,1.06.17,2.22,2.22,0,0,0,1.45-.39,2.12,2.12,0,0,0,.63-1.41l.29-2a3.73,3.73,0,0,1-1,.84A2.61,2.61,0,0,1,250,35a2.16,2.16,0,0,1-1.89-.88,3.9,3.9,0,0,1-.64-2.35,6.52,6.52,0,0,1,.58-2.6A5.62,5.62,0,0,1,249.73,27a4.15,4.15,0,0,1,2.61-.87,4.47,4.47,0,0,1,.87.1,5.15,5.15,0,0,1,.8.24l1-.34-1.38,9.31a3.37,3.37,0,0,1-.81,1.87m-.61-10.36a2.36,2.36,0,0,0-1.75.74,4.82,4.82,0,0,0-1.07,1.85,7.16,7.16,0,0,0-.35,2.15,3.3,3.3,0,0,0,.37,1.72,1.16,1.16,0,0,0,1,.62,2.09,2.09,0,0,0,1.2-.39,3.12,3.12,0,0,0,.9-.87l.82-5.5a1.85,1.85,0,0,0-1.15-.32"/><path class="cls-1" d="M258.39,33.67a.45.45,0,0,0,.07.28.19.19,0,0,0,.17.1.6.6,0,0,0,.35-.11,3.13,3.13,0,0,0,.44-.35l.2.37a3.17,3.17,0,0,1-.69.68,1.77,1.77,0,0,1-1.08.35,1.14,1.14,0,0,1-.78-.24.82.82,0,0,1-.22-.71c0-.26.16-1.25.4-3,.15-.93.32-2.17.52-3.7l-.95-.36.09-.52,2.19-.35.33.17-1,7.21Zm-.07-9.46a.81.81,0,0,1-.24-.6,1.09,1.09,0,0,1,.3-.78.94.94,0,0,1,.72-.33.81.81,0,0,1,.61.24.82.82,0,0,1,.23.58,1.17,1.17,0,0,1-.29.8,1,1,0,0,1-.77.33.76.76,0,0,1-.56-.24"/><path class="cls-1" d="M265.74,26.67a3.11,3.11,0,0,1,1.72-.56,1.65,1.65,0,0,1,1.32.53,2.5,2.5,0,0,1,.47,1.7,15.68,15.68,0,0,1-.34,2.35l-.06.35-.13.74a11.6,11.6,0,0,0-.24,1.86c0,.27.06.41.2.41a1.2,1.2,0,0,0,.72-.38l.18.4a1.54,1.54,0,0,1-.32.35,2.28,2.28,0,0,1-.61.39,1.73,1.73,0,0,1-.79.18.84.84,0,0,1-1-.94,12.8,12.8,0,0,1,.27-1.87l.14-.74.06-.37c.1-.55.19-1,.25-1.45a8.07,8.07,0,0,0,.09-1.16,1.64,1.64,0,0,0-.21-1,.87.87,0,0,0-.73-.27,2.27,2.27,0,0,0-1.37.61,5.7,5.7,0,0,0-1.3,1.46l-.75,5.55h-1.46l1-7.44-.75-.36.12-.59,1.88-.34.32.17-.2,1.85a5.77,5.77,0,0,1,1.5-1.46"/><path class="cls-1" d="M276.11,34.48a3.7,3.7,0,0,1-1.95.52,3,3,0,0,1-1.71-.46,2.87,2.87,0,0,1-1-1.23,4.24,4.24,0,0,1-.32-1.64,6.53,6.53,0,0,1,.59-2.75,5.17,5.17,0,0,1,1.63-2,3.76,3.76,0,0,1,2.29-.77,2.32,2.32,0,0,1,1.65.53,1.76,1.76,0,0,1,.55,1.36,2.31,2.31,0,0,1-.88,1.84A5.83,5.83,0,0,1,274.87,31a9.08,9.08,0,0,1-2.15.4,3.49,3.49,0,0,0,.36,1.86,1.48,1.48,0,0,0,1.4.79,3.16,3.16,0,0,0,1.35-.31,3.9,3.9,0,0,0,1.22-.9l.33.57a3.93,3.93,0,0,1-1.27,1.1m-2.1-7a4.12,4.12,0,0,0-.88,1.44,6.37,6.37,0,0,0-.38,1.7,5.17,5.17,0,0,0,1.62-.34,3.78,3.78,0,0,0,1.4-.87,1.74,1.74,0,0,0,.57-1.28,1.31,1.31,0,0,0-.28-.91,1,1,0,0,0-.78-.32,1.68,1.68,0,0,0-1.27.58"/><path class="cls-1" d="M284,34.48a3.7,3.7,0,0,1-2,.52,3,3,0,0,1-1.71-.46,2.87,2.87,0,0,1-1-1.23,4.24,4.24,0,0,1-.32-1.64,6.53,6.53,0,0,1,.59-2.75,5.26,5.26,0,0,1,1.63-2,3.79,3.79,0,0,1,2.3-.77,2.31,2.31,0,0,1,1.64.53,1.76,1.76,0,0,1,.55,1.36,2.31,2.31,0,0,1-.88,1.84A5.74,5.74,0,0,1,282.73,31a9.08,9.08,0,0,1-2.15.4,3.4,3.4,0,0,0,.37,1.86,1.45,1.45,0,0,0,1.39.79,3.2,3.2,0,0,0,1.36-.31,3.86,3.86,0,0,0,1.21-.9l.34.57a4,4,0,0,1-1.28,1.1m-2.1-7a4.12,4.12,0,0,0-.88,1.44,6.37,6.37,0,0,0-.38,1.7,5.17,5.17,0,0,0,1.62-.34,3.7,3.7,0,0,0,1.4-.87,1.74,1.74,0,0,0,.57-1.28,1.31,1.31,0,0,0-.28-.91,1,1,0,0,0-.78-.32,1.7,1.7,0,0,0-1.27.58"/><path class="cls-1" d="M290.05,27.3a3.77,3.77,0,0,1,1-.83,2.34,2.34,0,0,1,1.22-.34.83.83,0,0,1,.5.11l-.33,1.62a1.45,1.45,0,0,0-.75-.15,2.3,2.3,0,0,0-1.29.44,2.89,2.89,0,0,0-1,1.22l-.7,5.47h-1.48l1-7.41-.77-.38.11-.57,1.81-.35.31.18-.11,1.37-.08.61a4.09,4.09,0,0,1,.6-1"/><path class="cls-1" d="M295.29,33.67a.45.45,0,0,0,.07.28.19.19,0,0,0,.17.1.6.6,0,0,0,.35-.11,3.13,3.13,0,0,0,.44-.35l.2.37a3.17,3.17,0,0,1-.69.68,1.77,1.77,0,0,1-1.08.35,1.14,1.14,0,0,1-.78-.24.82.82,0,0,1-.22-.71c0-.26.16-1.25.4-3,.15-.93.32-2.17.52-3.7l-.95-.36.09-.52,2.19-.35.33.17-1,7.21Zm-.07-9.46a.81.81,0,0,1-.24-.6,1.09,1.09,0,0,1,.3-.78.94.94,0,0,1,.72-.33.81.81,0,0,1,.61.24.82.82,0,0,1,.23.58,1.17,1.17,0,0,1-.29.8,1,1,0,0,1-.77.33.76.76,0,0,1-.56-.24"/><path class="cls-1" d="M302.33,26.67a3.14,3.14,0,0,1,1.73-.56,1.67,1.67,0,0,1,1.32.53,2.56,2.56,0,0,1,.46,1.7,15.68,15.68,0,0,1-.34,2.35l-.06.35-.12.74a10.81,10.81,0,0,0-.25,1.86c0,.27.07.41.2.41a1.2,1.2,0,0,0,.72-.38l.19.4a1.64,1.64,0,0,1-.33.35,2.22,2.22,0,0,1-.6.39,1.76,1.76,0,0,1-.79.18c-.65,0-1-.31-1-.94a12.8,12.8,0,0,1,.27-1.87l.14-.74.06-.37c.11-.55.19-1,.25-1.45a8.07,8.07,0,0,0,.09-1.16,1.73,1.73,0,0,0-.2-1,.88.88,0,0,0-.73-.27,2.3,2.3,0,0,0-1.38.61,5.7,5.7,0,0,0-1.3,1.46l-.75,5.55h-1.46l1-7.44-.75-.36.13-.59,1.87-.34.32.17-.2,1.85a5.77,5.77,0,0,1,1.5-1.46"/><path class="cls-1" d="M312.92,37.29a4,4,0,0,1-1.55,1.05,5.36,5.36,0,0,1-1.78.32,5.69,5.69,0,0,1-1-.09,3.57,3.57,0,0,1-.77-.19l.33-1.24a5,5,0,0,0,.9.34,3.51,3.51,0,0,0,1.06.17,2.22,2.22,0,0,0,1.45-.39,2.11,2.11,0,0,0,.62-1.41l.3-2a3.73,3.73,0,0,1-1,.84,2.63,2.63,0,0,1-1.33.34,2.16,2.16,0,0,1-1.89-.88,3.9,3.9,0,0,1-.64-2.35,6.35,6.35,0,0,1,.58-2.6A5.62,5.62,0,0,1,309.88,27a4.11,4.11,0,0,1,2.61-.87,4.56,4.56,0,0,1,.87.1,5.15,5.15,0,0,1,.8.24l.95-.34-1.38,9.31a3.37,3.37,0,0,1-.81,1.87m-.62-10.36a2.35,2.35,0,0,0-1.74.74,4.7,4.7,0,0,0-1.07,1.85,7.16,7.16,0,0,0-.35,2.15,3.3,3.3,0,0,0,.37,1.72,1.14,1.14,0,0,0,1,.62,2,2,0,0,0,1.19-.39,3.3,3.3,0,0,0,.91-.87l.82-5.5a1.88,1.88,0,0,0-1.16-.32"/><path class="cls-1" d="M237.11,49.24c.83-1.82,1.39-3.07,1.65-3.76h3.29l-.06.66-1.37.17-.29,9.8,1.31.18-.07.6h-4.22l.06-.6,1.4-.18.35-6.79.2-3.12L238.2,49l-3.57,8-.83.11-1.26-7.89-.47-2.92-.63,3-1.64,6.91,1.55.18-.06.6h-4l.06-.6,1.28-.18,2.47-9.8-1.41-.17.09-.66h3.56L234.56,53l.2,1.57.67-1.53c.28-.69.84-1.95,1.68-3.77"/><path class="cls-1" d="M247.75,56.54a3.75,3.75,0,0,1-1.95.52,3,3,0,0,1-1.71-.47,2.7,2.7,0,0,1-1-1.23,4.19,4.19,0,0,1-.32-1.63,6.35,6.35,0,0,1,.59-2.75,5.17,5.17,0,0,1,1.63-2,3.7,3.7,0,0,1,2.29-.77,2.32,2.32,0,0,1,1.65.52,1.82,1.82,0,0,1,.55,1.37,2.34,2.34,0,0,1-.89,1.84A5.79,5.79,0,0,1,246.5,53a8,8,0,0,1-2.15.4,3.51,3.51,0,0,0,.37,1.87,1.48,1.48,0,0,0,1.4.79,3.18,3.18,0,0,0,1.35-.32,3.75,3.75,0,0,0,1.21-.9l.34.57a4,4,0,0,1-1.27,1.11m-2.11-7a4.25,4.25,0,0,0-.87,1.45,6.25,6.25,0,0,0-.39,1.69,5.44,5.44,0,0,0,1.63-.33,4.05,4.05,0,0,0,1.4-.87A1.76,1.76,0,0,0,248,50.2a1.33,1.33,0,0,0-.29-.92,1,1,0,0,0-.77-.31,1.74,1.74,0,0,0-1.28.57"/><path class="cls-1" d="M257.17,55.72q0,.39.24.39a1.19,1.19,0,0,0,.7-.39l.22.39a3.42,3.42,0,0,1-.67.62,1.68,1.68,0,0,1-1,.31c-.6,0-.9-.32-.9-1v-.34a3.94,3.94,0,0,1-1.08.94,2.72,2.72,0,0,1-1.44.38,2.13,2.13,0,0,1-1.87-.88,4,4,0,0,1-.63-2.34,6.41,6.41,0,0,1,.58-2.62A5.56,5.56,0,0,1,253,49a4.1,4.1,0,0,1,2.61-.86,4,4,0,0,1,1.15.18l.41-2.76-1-.26.13-.54,2.16-.28.34.2-1.6,10.84a.79.79,0,0,0,0,.17M255.42,49a2.32,2.32,0,0,0-1.74.75,4.64,4.64,0,0,0-1.06,1.84,7.15,7.15,0,0,0-.34,2.16,3.44,3.44,0,0,0,.36,1.72,1.12,1.12,0,0,0,1,.61,2.06,2.06,0,0,0,1.23-.41,3.11,3.11,0,0,0,.9-.91l.83-5.42a1.94,1.94,0,0,0-1.2-.34"/><path class="cls-1" d="M262.14,55.72a.57.57,0,0,0,.06.29.24.24,0,0,0,.18.1.71.71,0,0,0,.35-.11,3.84,3.84,0,0,0,.44-.35l.19.37a2.88,2.88,0,0,1-.68.67,1.71,1.71,0,0,1-1.08.35,1.19,1.19,0,0,1-.78-.23.8.8,0,0,1-.22-.72c0-.25.15-1.25.4-3,.14-.93.32-2.16.52-3.7l-.95-.35.09-.52,2.18-.36.34.17-1,7.22Zm-.07-9.46a.81.81,0,0,1-.24-.6,1.12,1.12,0,0,1,.3-.78,1,1,0,0,1,.71-.32.83.83,0,0,1,.62.24.81.81,0,0,1,.23.57,1.2,1.2,0,0,1-.29.81,1,1,0,0,1-.77.33.73.73,0,0,1-.56-.25"/><path class="cls-1" d="M269.42,49.14a2,2,0,0,0-1.35.54,3.6,3.6,0,0,0-.92,1.52,7,7,0,0,0-.33,2.24,3.52,3.52,0,0,0,.43,2,1.39,1.39,0,0,0,1.24.66,2.38,2.38,0,0,0,1.1-.24,5.05,5.05,0,0,0,1-.72l.3.57a4,4,0,0,1-1.14,1A3.43,3.43,0,0,1,268,57a2.44,2.44,0,0,1-2-.91,4,4,0,0,1-.73-2.54,6.43,6.43,0,0,1,.53-2.51A5.3,5.3,0,0,1,267.33,49a3.69,3.69,0,0,1,2.42-.83,5,5,0,0,1,.93.09,3.09,3.09,0,0,1,.81.26L271.07,50l-.26-.09a2.53,2.53,0,0,0-1.39-.78"/><path class="cls-1" d="M274.77,55.72a.56.56,0,0,0,.07.29.24.24,0,0,0,.18.1.71.71,0,0,0,.35-.11,3.15,3.15,0,0,0,.43-.35l.2.37a2.88,2.88,0,0,1-.68.67,1.71,1.71,0,0,1-1.08.35,1.19,1.19,0,0,1-.78-.23.8.8,0,0,1-.22-.72c0-.25.15-1.25.4-3,.14-.93.32-2.16.52-3.7l-1-.35.09-.52,2.18-.36.34.17-1,7.22Zm-.07-9.46a.85.85,0,0,1-.23-.6,1.12,1.12,0,0,1,.3-.78.94.94,0,0,1,.71-.32.79.79,0,0,1,.61.24.78.78,0,0,1,.24.57,1.16,1.16,0,0,1-.3.81,1,1,0,0,1-.76.33.75.75,0,0,1-.57-.25"/><path class="cls-1" d="M282,48.73a3.09,3.09,0,0,1,1.73-.56,1.65,1.65,0,0,1,1.32.52,2.54,2.54,0,0,1,.46,1.7,15.09,15.09,0,0,1-.33,2.35l-.07.36-.12.73a11.6,11.6,0,0,0-.24,1.86c0,.28.06.42.19.42a1.22,1.22,0,0,0,.73-.39l.18.4a1.77,1.77,0,0,1-.32.36,3.21,3.21,0,0,1-.61.39,1.86,1.86,0,0,1-.79.17c-.64,0-1-.31-1-.93a13.42,13.42,0,0,1,.28-1.88l.14-.73.06-.37c.1-.56.18-1,.25-1.45a8.17,8.17,0,0,0,.09-1.16,1.67,1.67,0,0,0-.21-1,.87.87,0,0,0-.73-.27,2.31,2.31,0,0,0-1.37.61,5.58,5.58,0,0,0-1.3,1.47l-.75,5.54H278.2l1-7.43-.75-.37.12-.58,1.87-.34.33.17-.2,1.84A5.85,5.85,0,0,1,282,48.73"/><path class="cls-1" d="M292.42,56.54a3.75,3.75,0,0,1-1.95.52,3,3,0,0,1-1.71-.47,2.7,2.7,0,0,1-1-1.23,4.19,4.19,0,0,1-.32-1.63A6.35,6.35,0,0,1,288,51a5.17,5.17,0,0,1,1.63-2,3.7,3.7,0,0,1,2.29-.77,2.32,2.32,0,0,1,1.65.52,1.82,1.82,0,0,1,.55,1.37,2.34,2.34,0,0,1-.89,1.84A5.79,5.79,0,0,1,291.17,53a8,8,0,0,1-2.15.4,3.51,3.51,0,0,0,.37,1.87,1.48,1.48,0,0,0,1.4.79,3.18,3.18,0,0,0,1.35-.32,3.75,3.75,0,0,0,1.21-.9l.34.57a4,4,0,0,1-1.27,1.11m-2.11-7a4.25,4.25,0,0,0-.87,1.45,6.25,6.25,0,0,0-.39,1.69,5.44,5.44,0,0,0,1.63-.33,4.05,4.05,0,0,0,1.4-.87,1.76,1.76,0,0,0,.57-1.28,1.33,1.33,0,0,0-.29-.92,1,1,0,0,0-.77-.31,1.74,1.74,0,0,0-1.28.57"/></g></g></svg> </a> </div> <div><a href="http://www.nasonline.org/" rel="noreferrer" target="_blank" class="global-footer__org"><img src="data:image/png;base64,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" alt="NAS Logo" width="17" height="17"> <span> National Academy of Sciences </span></a> <a href="https://www.nae.edu/" rel="noreferrer" target="_blank" class="global-footer__org"><img src="data:image/png;base64,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" alt="NAE Logo" width="17" height="17"> <span> National Academy of Engineering </span></a> <a href="https://nam.edu/" rel="noreferrer" target="_blank" class="global-footer__org"><img src="data:image/png;base64,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" alt="NAM Logo" width="17" height="17"> <span> National Academy of Medicine </span></a></div></div> <div class="global-footer__links"><ul class="global-footer__nav"><li><a rel="" title="" href="//www.nationalacademies.org/about" target="_self"> About Us </a></li><li><a rel="" title="" href="//www.nationalacademies.org/our-work" target="_self"> Our Work </a></li><li><a rel="" title="" href="//www.nationalacademies.org/events" target="_self"> Events </a></li><li><a rel="" title="" href="//www.nationalacademies.org/contact-us" target="_self"> Contact Us </a></li><li><a rel="" title="" href="//www.nationalacademies.org/opportunities" target="_self"> Opportunities </a></li><li><a rel="" title="" href="//www.nationalacademies.org/publications" target="_self"> Publications </a></li><li><a rel="" title="" href="//www.nationalacademies.org/about/visiting-us" target="_self"> Visit </a></li><li><a rel="" title="" href="//www.nationalacademies.org/about/operating-status" target="_self"> Current Operating Status </a></li><li><a rel="" title="" href="//www.nationalacademies.org/subscribe" target="_self"> E-Newsletters </a></li></ul> <div class="global-footer__social"><p> Connect With Us </p> <ul><li><a href="https://www.facebook.com/NationalAcademies/" target="_self" class="connect-facebook"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class=""><path fill-rule="evenodd" d="M20 9.375h-2.222c-.334 0-1.111.531-1.111 1.125v2.25H20v3.375h-3.333V24h-3.334v-7.875H10V12.75h3.333V10.5c0-2.482 2.18-4.5 4.515-4.5H20v3.375"></path></svg></a></li><li><a href="https://twitter.com/TheNASEM" target="_self" class="connect-twitter"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class=""><path fill-rule="evenodd" d="M24 9.775a7.238 7.238 0 01-2.121.598 3.787 3.787 0 001.625-2.096 7.253 7.253 0 01-2.347.92A3.65 3.65 0 0018.461 8c-2.04 0-3.695 1.697-3.695 3.787 0 .298.033.586.096.863-3.07-.157-5.793-1.665-7.615-3.956a3.853 3.853 0 00-.499 1.904c0 1.313.853 2.472 1.845 3.151-.606-.02-1.473-.191-1.473-.475v.05c0 1.833 1.072 3.363 2.761 3.712-.31.086-.736.133-1.072.133a3.99 3.99 0 01-.746-.07c.47 1.505 1.81 2.6 3.425 2.632A7.343 7.343 0 016 21.299 10.277 10.277 0 0011.66 23c6.795 0 10.51-5.77 10.51-10.774 0-.163-.005-.328-.013-.491A7.588 7.588 0 0024 9.775"></path></svg></a></li><li><a href="https://www.linkedin.com/company/the-national-academies" target="_self" class="connect-linkedin"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class=""><path fill-rule="evenodd" d="M7 23V10.533h3.4V23H7zm12.467-12.467c2.558 0 4.533 2.034 4.533 5.665V23h-3.4v-6.347c0-1.586-.779-2.679-2.192-2.679-1.082 0-1.94.736-2.223 1.443-.097.251-.118.608-.118.959V23h-3.4s.088-11.333.035-12.467h3.365l-.04 2.267c.516-1.133 1.335-2.267 3.44-2.267zM10.4 7.7a1.7 1.7 0 11-3.4 0 1.7 1.7 0 013.4 0z"></path></svg></a></li><li><a href="http://www.nationalacademies.org/news.xml" target="_self" title="Share our site" class="connect-rss"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class=""><path d="M11.85 20.537a2.425 2.425 0 11-4.85 0 2.425 2.425 0 014.85 0zm6.65 1.79c-.316-5.854-5.005-10.548-10.864-10.865a.605.605 0 00-.636.605v1.82c0 .32.246.586.564.607a8.484 8.484 0 017.904 7.904c.02.318.288.564.607.564h1.82c.346 0 .624-.29.605-.636zm5.462.01C23.644 13.484 16.52 6.32 7.625 6A.605.605 0 007 6.606v1.82c0 .327.259.593.585.606 7.238.297 13.048 6.108 13.345 13.345.013.326.28.585.606.585h1.82a.605.605 0 00.606-.625z"></path></svg></a></li><li><a href="//www.nationalacademies.org/subscribe" target="_self" title="Subscribe" class="connect-email"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class=""><path fill-rule="evenodd" d="M6 12.964v4.569c0 .296.197.386.439.2l2.822-2.15c.243-.184.243-.484 0-.669l-2.822-2.15c-.242-.185-.439-.095-.439.2zM7.125 9C6.506 9 6 9.601 6 10.071l8.514 6.455a.775.775 0 00.882.002L24 10.07C24 9.601 23.494 9 22.875 9H7.125zm13.613 6.584l2.822 2.15c.243.185.44.095.44-.201v-4.569c0-.295-.197-.385-.44-.2l-2.822 2.15c-.242.185-.242.485 0 .67zM18.26 16.8l-2.822 2.15a.764.764 0 01-.879 0l-2.822-2.15a.765.765 0 00-.88-.001L6 20.495v.29c0 .471.506 1.072 1.125 1.072h15.75c.619 0 1.125-.6 1.125-1.071v-.29L19.141 16.8a.767.767 0 00-.88.001z"></path></svg></a></li></ul></div> <div class="global-footer__legal"><div><button class="button button--icon button--reverse button--secondary"> <a href="https://www8.nationalacademies.org/AcademyGiving/nas/nasform.aspx ">Donate Today</a> <span class="button__icon"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 30 30" class=""><path d="M17.885 10.708a1 1 0 111.412-1.416l5.624 5.608-5.616 5.732a1 1 0 11-1.428-1.4l4.228-4.316-4.22-4.208z"></path><path d="M23.07 14a1 1 0 010 2H7a1 1 0 010-2h16.07z"></path></svg></span></button></div> <div><ul><li><a rel="" title="" href="//www.nationalacademies.org/legal/privacy" target="_self"> Privacy Statement </a></li><li><a rel="" title="" href="//www.nationalacademies.org/legal/policy" target="_self"> DMCA Policy </a></li><li><a rel="" title="" href="//www.nationalacademies.org/legal/terms" target="_self"> Terms of Use </a></li><li><a rel="" title="" href="//www.nationalacademies.org/site-map" target="_self"> Site Map </a></li></ul> <p class="copyright"><a rel="" title="" href="//www.nationalacademies.org/legal" target="_self"> Copyright © <script type="text/javascript">  </script> National Academy of Sciences. All Rights Reserved. </a></p></div></div></div></div></footer> <script src="//nap.nationalacademies.org/includes/js/jquery.dlmenu.js"></script> <script src="//nap.nationalacademies.org/includes/js/jquery.placeholder.js"></script>  <script> // Save to MyNAP handler $('a.saveit').one('click', function(e) { e.preventDefault(); $.getJSON('/napsave.php', { type: 'shelf', r: $(this).data('recordid') }, function(response) { $(e.target) .toggleClass('saveit saveit_active') .attr('href', '/mynap.php') .text('Added to Bookshelf'); }); }); </script>  <script src="https://cdn.cookielaw.org/scripttemplates/otSDKStub.js" type="text/javascript" charset="UTF-8" data-domain-script="5639f7b9-d1de-4e1d-9f2f-e86c3f24727b" ></script> <script type="text/javascript"> function OptanonWrapper() { } </script>  <script src="/includes/js/popper.js"></script> <script src="/vendor/bootstrap/3.1.1/bootstrap.min.js"></script> <script src="/includes/js/jquery.dotdotdot.min.js" type="text/javascript"></script> <script src="/includes/js/typeahead.bundle.min.js"></script>  <script src="/includes/js/svg4everybody.ie8.min.js"></script> <script> $(document).ready(function(){ // Activate Carousel with a specified interval $("#myCarousel").carousel({interval: 9000, pause: "hover", keyboard:true}); // Enable Carousel Indicators $(".item1").click(function(){ $("#myCarousel").carousel(0); }); $(".item2").click(function(){ $("#myCarousel").carousel(1); }); $(".item3").click(function(){ $("#myCarousel").carousel(2); }); // Enable Carousel Controls $(".carousel-control-prev").click(function(){ $("#myCarousel").carousel("prev"); }); $(".carousel-control-next").click(function(){ $("#myCarousel").carousel("next"); }); }); </script> <script> $(document).ready(function() { var titleSearch = new Bloodhound({ datumTokenizer: function(d) {return Bloodhound.tokenizers.obj.whitespace(d.title);}, queryTokenizer: Bloodhound.tokenizers.whitespace, limit: 30, // prefetch: { // url: '/data/scope/books', // }, remote: { url: '?get=search&term=%QUERY', wildcard : '%QUERY', filter: function(response) { if( response.hits > 1){ return response.result; } else { var result= {}; return result; } } } }); titleSearch.initialize(); $('#inputsearch').typeahead({ 'highlight': true, 'hint': false, 'minLength': 3 }, { name: 'books', displayKey: 'title', source: titleSearch.ttAdapter(), templates: { header: '<div class="suggestion-inner"><h4> Suggested Title Results... </h4></div>', suggestion: function(item) { var title = item.title; if (item.year > 0) { title += ' (' + item.year + ')'; } var cover = '//nap.nationalacademies.org/images/'; var coll_id = item.path.split('=').pop(); if (coll_id > 0 ) { cover += 'collections/' + coll_id + '.png'; } else { cover += 'cover.php?id=' + item.record_id + '&type=tinycov'; } template = '<div class="suggestion-inner" id="' + title + '"><div class="img-container img-circle"><img src="' + cover + '"></div><p>' + title + '</p></div>' return template; } } }).on('typeahead:selected', function(event, item) { var url; if (item.record_id === '0000') { url = item.path; } else { url = 'https://nap.nationalacademies.org/catalog.php?record_id=' + item.record_id; } // trackEvent('homepage', 'autocomplete', item.title); // trackEvent('homepage', 'search', $('#inputsearch').typeahead('val')); window.location = url; ttvalue = $('#inputsearch').typeahead('val'); tttitle = item.title; window.dataLayer = window.dataLayer || [];dataLayer.push({ 'searchTitle' : tttitle, 'event' : 'searchTypeahead', }); }); $('.btn-searchhome').appendTo('.twitter-typeahead'); </script> <script> $('.recommendations').on('click', 'a', function(e) { var rowTitle = 'Recommended for You'; var position = ($(this).closest('.rfy-tile').index() + 1).toString(); var element = $(this).data('alias'); var title = $(this).data('title'); dlPush(rowTitle, position, element, title); }); $('.book-row .book-tile a').on('click', function(e) { var rowTitle = $(this).closest('.book-row').data('title'); var position = ($(this).closest('.book-tile').index()).toString(); var element = $(this).data('alias'); var title = $(this).data('title'); dlPush(rowTitle, position, element, title); }); $('.sc-row .sc-tile').on('click', 'a, .sc-outer, .sc-inner h4, .sc-inner .sc-desc', function(e) { var rowTitle = $(this).closest('.sc-row').data('title'); var position = ($(this).closest('.sc-tile').index()).toString(); var element = $(this).data('alias'); var title = $(this).closest('.sc-tile').find('a').data('title'); dlPush(rowTitle, position, element, title); }); $('.mm-row .mm-tile a').on('click', function(e) { var rowTitle = $(this).closest('.mm-row').data('title'); var position = ($(this).closest('.mm-tile').index()).toString(); var element = $(this).data('alias'); var title = $(this).data('title'); dlPush(rowTitle, position, element, title); }); $('#dl-menu').dlmenu({ animationClasses: { classin: 'dl-animate-in-5', classout: 'dl-animate-out-5' } }); $('.truncate').dotdotdot({ watch: 'window', lastCharacter: { remove: [' ', ',', ';', '.', '!', '?'] } }); $(document).on('click', '.sc-inner, .sc-outer, .rfy', function() { window.location = $(this).find('a').attr('href'); }); $('.col-sc').hover(function() { $(this).find('.sc-inner').filter(':not(:animated)').animate({ top: '0px' }); }, function () { $(this).find('.sc-inner').animate({ top: '190px' }); }); $('.close, .overlay').click(function() { $('#bbt-sidebar').animate({ width: 'toggle' }); $('.overlay').fadeOut(); }); $('#subscribe-form').on('submit', function(event) { if ($('#email').val().match(/@/)) { $('#subscriber-key').val(email); } else { event.preventDefault(); $('#email') .val('') .attr('placeholder', 'The email address you entered is invalid.') .focus() .closest('.input-group') .addClass('has-error'); setTimeout(function() { $('#email') .attr('placeholder', 'Sign up for e-mail updates') .closest('.input-group') .removeClass('has-error'); }, 5000); } }); function dlPush(rowTitle, position, element, title, event){ window.dataLayer = window.dataLayer || [];dataLayer.push({ 'rowTitle' : rowTitle, 'position' : position, 'element' : element, 'title' : title, 'rowpage' : 'homepage', 'event' : 'rowSelect', }); } </script> <script src="https://s3-us-west-2.amazonaws.com/s.cdpn.io/3/jquery.color-RGBa-patch.js"></script> <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.5.2/jquery.min.js"></script> <script> $(function() { var $el, leftPos, newWidth, $mainNav = $("#local-nav-nap"); $mainNav.append("<li id='magic-line'></li>"); var $magicLine = $("#magic-line"); $magicLine .width($(".current_page_item").width()) .css("left", $(".current_page_item a").position().left) .data("origLeft", $magicLine.position().left) .data("origWidth", $magicLine.width()); $("#local-nav-nap li a").hover(function() { $el = $(this); leftPos = $el.position().left; newWidth = $el.parent().width(); $magicLine.stop().animate({ left: leftPos, width: newWidth }); }, function() { $magicLine.stop().animate({ left: $magicLine.data("origLeft"), width: $magicLine.data("origWidth") }); }); });</script>  </body> </html>

CINXE.COM

The National Academies Press